《单调性与最大（小）值》教学设计2
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约3120字。
　　单调性与最大（最小）值
　　【教材分析】
　　最值问题是生产、科学研究和日常生活中常遇到的一类特殊的数学问题，是高中数学的一个重点，它涉及到高中数学知识的各个方面，解决这类问题往往需要综合运用各种技能，灵活选择合理的解题途径.本节课利用单调性求函数的最值，目的是让学生知道学习函数的单调性是为了更好地研究函数.利用单调性不仅仅确定函数的值域、最值，更重要的是在实际应用中求解利润、费用的最大与最小，用料、用时的最少，流量、销量的最大，选取的方法最多、最少等问题.
　　【教学目标】
　　1.理解并掌握函数最大(最小)值的概念及其几何意义，并能利用函数图象及函数单调性求函数的最大(最小)值.
　　2.在求函数最大(最小)值中，提高分析问题、创造地解决问题的能力，渗透数形结合的数学思想.
　　【教学重难点】
　　教学重点:理解函数最大(最小)值.
　　教学难点:利用函数的单调性求函数最大(最小)值.
　　【教学设计建议】
　　一、导入新课
　　1、生活中，有很多的函数变化的模型.比如某段时间的股市变化图和某市一天24小时内的气温变化图等，分别说出股票综合指数和气温随时间变化的特点，如相应图象在什么时候递增或递减，有没有最大(最小)值等.
　　2、前面我们学习了函数的单调性，知道了在函数定义域的某个区间上函数值的变化与自变量增大之间的关系.从函数图象的角度很容易直观的知道函数图象的最高点（或最低点），如何从解析式（函数值）的角度认识函数的最大(最小)值呢？
　　【设计意图：根据生活中的实际例子认识函数图象的变化特征，复习函数的单调性，引出函数的最大(最小)值，并使学生分别从函数图象的角度和从解析式的角度刻画函数的最大(最小)值,激发学生探究函数最大(最小)值的概念及其几何意义的兴趣.】
　　二、探索新知
　　（一）画出下列函数的图象，指出图象的最高点或最低点，并说明它能体现函数的什么特征？
　　①&& ②&& ③
　　（二）观察上述三个函数的图象，如何用数学符号解释：相应函数的图象有最高点或者最低点？
　　函数图象最高点的纵坐标是所有函数值中的最大值,即函数的最大
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站内部分资源并非原创，若无意中侵犯到您的权利,敬请来信联系我们。杨威：股海捕鱼（五）微积分股票个股和大盘分析
日期:01-13-2016 | 阅读:2,805 views | 分类:&|
微积分与股票的联系，微积分中的导数，凹凸性，极值点，拐点，单调性，在研究股票的拉升力度，封板力度，持币等待时间，判断主力做多意愿强弱等方面都有体现，如果能结合大盘趋势，个股趋势，成交量，价格来研究走势图形，效果非常好。
来看看下面几种涨停板的情况：
1、涨停封板有一段凸弧，不好，封板无力度，容易开板。
2、凹增的弧发生了变化，封板资金稍微有些犹豫。
3、凹增涨停封板
4、直线封涨停板
从拉升的增速来看，3&4&2&1，理论上而言，3是以指数增速封板的，是拉升最强悍的，而实际上，图4直线拉升封板的往往封板最坚固，开板的可能性最小。
锯齿分时走势
如果分时线像锯齿，振幅很小，几乎都是“横线”和“折线”，不光滑，很少有地方“可导”，振幅也很小，这样的股票不要参与，让机构和社保去玩吧，因为他可能一年的价格都没有什么变化。
杂乱分时走势
从图形上看，极小值和极大值点有很多处，这说明，当你持币的时候，需要“等”，因为好的买点一天只有一个，股票的魅力在于等待，当你持币的时候，你在“等”买点，当你持股时你在“等”卖点，“等”贯穿始终。
凸弧分时走势
红圈内是一段凸弧，凸弧一般意味着会加速下跌，而且是“凸减”，流畅的弧线总是出现在大盘股，小盘股的曲线一般都是折线，不流畅。红色箭头对应的这个点是一个“捣鬼点”。数学上看，这个点是“拐点”，图形“凸减”突变成了“凹增”，这不是自然的力量，这是资金运作留下的痕迹。剧烈改变大盘股的凹凸性，需要大资金人为改变，我们可以从图形上看出主力是否强悍和做多的意图是否强烈。
资金拉升痕迹
1，2，4出现转折尖角的位置，都有明显人为操控的痕迹，就是有资金在拉升，在做图形，尤其是2最不自然，如果个股的走势出现那种心惊肉跳的转折点，那就是大资金在人为捣鬼，应该跟进，3是一段横盘洗筹。
哪些涨停次日上涨的概率大？哪些洗盘效果好？假设都是行情初期的第一个涨停，板上的封单都是20万手。
日期:01-12-2016 | 阅读:3,847 views | 分类:&|
股市中最重要的股票指标是什么？用一个字表达，我认为是：势！
“量和价”是我们比较关注的指标，但比二者还要重要的指标是：“势”。“势”即趋势也，“趋势”是一种客观存在，而明天的涨跌是一种主观判断。在买卖一只股票的时候，最先要判断的是“趋势”，“势”的重要性排在“量、价”的前面，所以是“势、量、价”。只要趋势判断对了，就好办了。如果是升势，那么任何时候买入都是正确的；如果是跌势任何时候卖出都是对的。
很多散户迷恋抄底，这是非常荒唐的，底一般只有一个，很难抄到。一个月只有一个底，一年只有一个底。你愿意用一年来等一个“底”吗？那没有意义。很多人即使抄到了底，依然拿不住，还不是几天就全部卖出了，抄底有何用呢？
道琼斯理论的核心是趋势理论：趋势一旦形成，将不易改变。
那么，怎样判断股票趋势呢？趋势分为大盘趋势和个股趋势，可以通过均线来判断。
当多条均线开始平行上升（也称多头排列），那么可以判断为升势，否则称为跌势（空头市）趋势分为短期趋势和长期趋势，短期趋势看5日线，10日线，20日线，长期趋势看30日线60
日线，120日线。
趋势分三种情况：升势，跌势，不明势。只能买处于升势的股票，不要买跌势的股票，不要买趋势不明的股票。如果说“势”是客观存在，那么次日的走势就是主观判断，是臆测。如果你想买一只股票，应该对这只股票次日的走势有个预测，通常预测情况也是3种预判，看涨，看跌，看不明白。
趋势3种 + 次日预判3种 = 9种情况，我们只能买升势+次日看涨这一种情形。
至于怎样预判一只股票次日的走势，要结合大盘，消息面，量价，技术指标如MACD，那些我会在后面再提及。综合起来一句话，只买升势的，而且第二天看涨的股票。
日期:01-12-2016 | 阅读:2,784 views | 分类:&|
股票交易10次盈4次就够了，盈率比胜率重要！
一直以来，和股友们交流股票的时候，他们喜欢问我，你操作成功的概率有多大？我回答：“有六七成吧，牛市会高一点”。朋友们通常对我的获胜概率有点失望，也许他们心中的股票高手应该是十拿八九稳才对。
追求高胜率（操作成功率）是我们散户的一大通病。这么说吧，10次操作，我只要成功4次，失败6次，通常我也能赚点。
为什么呢？成功的4次每次赚7%以上，获利28%，失败的6次每次亏4%，亏24%，这样一算，还有约4%左右的收益，10次交易如果能获得4%的收益，这已经非常可观了，银行定期存一年利息还不到2%呢，我不能保证在每十次交易中都能稳定获利4%，说不定是赚10%，20%，也说不定是亏20%。
每次获胜的操作能赚多少，这叫盈率，盈率要越大越好，通俗一点说，当你要买入一只股票的时候，你要问你自己，这只股票的收益会达到7%吗？会达到10%吗？会达到15%吗，如果这次操作你是冲着3%去的，那就很危险了，不值得冒险。
世间万物，都具有一个原则，即测不准原理，那只是一个理论。但从概率的角度，股票可以用数学方法预测，达到概率获胜，比如澳门赌场里面的百家乐，胜的概率比赔的概率多出1%，葡京酒店就可以百年不倒了。
中国有句古话，叫红颜多薄命，其实，这是违背事实的，应该说红颜多好命，说这话的人多少有一些嫉妒的成分在里面，好比有时我们说人家高分低能，不过是弱者的遮羞布而已。大多数红颜命好的很，活得很精彩。
在现实生活中，美女大多数都能嫁得好，原因在于，她们见多识广，她们要求高，他们心理预期高，让屌丝无机可乘，条件不好的不会托付。买股票也是如此，高回报的股票才下手，如果你觉得会有15%以上的涨幅你才考虑买进，如果涨幅很小，或者连涨的希望都没有，你还买它干嘛，不如空着。
因此，买入要非常谨慎，绝不会轻易出手，也不要随便为一点点的蝇头小利去冒险。
日期:01-01-2016 | 阅读:3,175 views | 分类:&|
股票投资是所有投资中门槛最低而赚钱最难的行当。与此同时，做股票的人有个特点，就是赚钱的时候到处说，亏钱的时候不吭声。
以前，不做股票的人和股票做不好的人问我：“你股票做的怎样？”，我一般是回答：“以亏为主”、“做的一般”。当然，和懂股票的人谈股票，我不会这样回答，我会认真探讨。
因为你如果回答，赚了多少云云，对方也许会想，“妈的，你赚这么多，也不见请我喝酒呀”，或者想“为什么我亏的这么多，而你能赚，糊弄谁啊”。而且，当我知道这个问我的人股票长期亏损的时候，我更愿意回答“以亏为主”，因为这样能安抚他，能引起他的共鸣。
接着，他会说，这股市真不是人做的，是什么王八羔子在管股市，XXX&￥%**%…………%￥
我说对啊，简直不是他妈人干的事啊。于是，气氛融洽，交谈亲切。
我有一个简单的方法，很容易衡量一个人是否能赚到钱。就是：他持续呆在股市的时间有多长。
如果一个人做了一年、两年或者几个月的股票，突然离开了股市，9成可以断定，他输着离开，黯然离去。我从来不相信“见好就收”这句鬼话，我不相信一个人在股市中赚钱赚的好好的，突然间说赚够本了离开了，说见好就收，谁信呢？
古语有云：人之欲望，沟壑难填，人的贪欲是很难满足的。
如果一个人在股市做了多年，比如5年，10年，经历了一轮完整的牛市和熊市，他还在，他一直在，他从来不曾离去，那么，不用问，他是盈利的，就这么简单。
所谓的“在”，所谓的“在股市”，不是说他的股票十年来一直被套着，不闻不问，这不是“在”，我说的“在”指的是：多年来，他一直在操作、在关注、在折腾、在花时间。
那么会不会人今年亏，明年亏，后年亏，年年亏，还在股市里面呢？从概率的角度上说，有，及少。
一个正常人，如果他的钱不是人家送的，不是浪打来的，如果他每年在股市上输，自己辛辛苦苦赚来的钱，一天就轻飘飘的输掉几个月的工资，我想，他会有剁手的冲动，他会黯然离去。
说了半天，就是判断一个人能否持续在股市盈利，那不是听他怎么说，而应该由他持续做股票的时间来进行衡量，时间越长的，赚钱的可能性越大。另外，假如能观察他的“吃穿住用行是否发生巨大提升来判断”，会更准确一些。我的同事C姓老师，做股票接近25年时间，一直在，从来不曾离去，他是股市的大赢家，而有的人呢，几年时间都不在股市，进来玩一年，再出去几年，再进来一年，再出去，我知道，这不用说，他输，他做不好。
当然了，也有人，也是长时间持续在股市折腾的，但他从来不输，每年稳中赚钱，这样的人也有，还不少，比如基金经理，私募经理等等，因为他们是拿工资的嘛。即便旗下的基金产品再怎么亏，他们也有工资拿，旱涝保收，这种情况，不在我要说的之列。是的，他们一边亏着投资者的钱，还一边拿着投资者的工资。难怪那么多人考大学要读金融专业，美着呢。如果让我从上一次大学，我就不学枯燥的数学啦，我要学金融。
日期:12-31-2015 | 阅读:2,827 views | 分类:&|
本人是在大学教数学，发现股市中的很多问题与数学有着微妙的联系，尤其是与微积分和概率论有非常密切的联系，本文是我闲来无事发表的，欢迎交流，具有不同观点的，可以一笑置之，勿要上了脾气，对身体不好。
2001年，经济学家吴敬琏在央视说：中国股市连一个规范的赌场都不如。道出了中国A股的本质。坊间说A股是1赚2平7亏，我感觉这种说法是错误的。据我的所见和观察，发现A股中只有约5%的人赚钱，95%的人亏损。股市中不存在“平”，因为股票占用了资金，资金具有机会成本，所谓的“平”，其实也是亏。
只有5%的人能获胜
没错，我发现股市中只有5%的人能赚钱，而且是爆赚，原因简单，95%的人在亏，那么多钱亏给谁了？亏的钱一部分是券商的佣金抽走了，一部分是国家税收带走了，一部分是指数涨跌蒸发了，还有一部分就是被5%的人高手赚走了。
我的学生中有人来问我股票的是后我最常说的是：“远离股市，远离毒品”，“远点，你先把书念完再说吧”。因为，股市不创造财富，股市只转移财富。那么，能够获利的5%是因为运气好呢，还是因为所谓的技术高超而掌握了股市的真谛？换而言之，也就是这个获利的5%的人，是怎样构成的，弄清这个问题非常的重要。
问题可以这样表述，如果这里有100个做股票的人：
情况A：今年是这5个人获利，明年是那5个人获利。
情况B：今年是这5个人获利，明年还是这5个人获利。
要弄清这个问题不难，没有调查就没有发言权。我这些年认识了很多投资股票的朋友，我有结论，结论是：情况B，也就是5%的人能够获利，不是因为他的运气好，而是因为他摸清了股票的规律，有幸成为了那部分能稳定获利的人。
与房产投资一样，股票投资是一种比较普遍的投资行为，以我周围的同事和朋友的投资情况来看，也符合这个5%定律。我琢磨过接近100人做股票的朋友，通过平时交谈和了解的情况，发现能够从股市中稳定取胜的人非常少，只有三四个人，这些朋友中，一个是C姓老师，一个是在下me，还有两名朋友因股票技术一般，另外，是否真的能从股市盈利我还不能百分之百的确定，所以不列出。
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以上网友发言只代表其个人观点，不代表新浪网的观点或立场。&p&我以前回答过类似的问题，可参考&/p&&p&&a href=&/question//answer/& class=&internal&&盛京剑客：作为一个期货初学者，在众多技术指标和各种理论中，哪些指标是值得学习研究而那种理论的方法值得掌握？&/a&&/p&&blockquote&其实把你的问题浓缩下，你是在问研究方向的问题&br&但却不知道MACD，RSI，KDJ…到底哪种适用，道氏，波浪，江恩，哪个又更值得深入...
&br&可以说，这些都是“目”，不是“纲”，只是实现目标的手段。&br&我在这里再透露点“干货”&br&做交易一定要明白投资获利的基本原理和本质是什么。&br&向着这个要素去努力，方向就对了，否则只能在外围打转转......
如果你不清楚本质要素，在江恩、波浪上努力，你努力的越久，你就偏离的越远~~这样的人我见的很多，迷信于预测，整天神叨叨的，呵呵&br&投资获利原理是什么？&br&投资获利原理再简单不过了，相信做过一段时间的人都懂，无非就是使获利最大化，使损失最小化，如果提炼一下，其中有三要素：1.赢率 2.获利 3.损失&br&赢率越高越好，获利越大越好，损失越小越好。&br&比如巴菲特，整天看财报，林奇整日做研究，啥目的？不就是通过阅读、拜访、研究发现符合这三点的标的么。巴菲特常说：第一条，不要亏损，第二条，要记住第一条。这话是不是把，赢率越高越好，获利越大越好，损失越小越好三要素都涵盖了？&br&孙子兵法上说：“古之所谓善战者，胜于易胜者也”，对付易胜者有什么好处？赢率特高，损失最小，获利较大，盈亏比特高。如果有若干个这样的弱敌，可能战胜每个敌人的获利不是很多，可是把他们一个接一个的轻松战胜，积小胜为大胜，那么实际上要比战胜强敌赢率高、获利高、损失小。&br&做研究的时候往这三点努力就对了&br&开始的时候，建议采用最常见的交易系统，只要这个系统期望值为正，逻辑上没有大的缺陷，那么就值得一做。然后，从这三个要素上不断的增强系统。&br&举例，你发现你的赢率不高。你经过研究，发现你的很多亏损仓位都是逆势开仓的，那么你就可以用一根长期均线来过滤掉逆势的信号。从而一定程度上提高赢率。&br&比如，你发现你的盈亏比太低了，经过研究，你发现你的交易标的常常出现大波段，而你的止盈点太紧了，造成频繁的平仓。这样的话，你可以调高止盈阈值扩大盈亏比。&br&又比如，你通过大量的数据研究，年度ROE大于10%的股票具有优势，如果采用你现有的交易系统操作要比你随机选股好的多，那么就可以将基本面选股融合进来，提高“三要素”&br&如果你在波浪、江恩中发现了能够增强三要素的灵感，那么你就可能独创出自己特有的交易系统，到时候那就是你自己的降龙十八掌了......&br&但要注意，这三者在某些系统中是有一定关系的。比如有时候你减小止损，会导致赢率降低，放大每笔收益，又会导致损失加大。总之，你要多多测试，找到三者较为平衡的，自己能够接受的搭配。&br&希望对你有帮助&/blockquote&&p&我提到过三要素：1.赢率 2.获利 3.损失&/p&&p&&b&考虑的灵感就是反复琢磨如何提升、整合这三者。甚至可以大开脑洞借助与金融毫不相关的知识达到目的。&/b&&/p&&p&&br&&/p&&p&我相信任何一个热爱交易的人都会认同彼得林奇所说的：他24小时都想着交易&/p&&p&我也经历过多个问题萦绕心头的阶段，经历过交易系统反复修改的阶段、经历过开发个性化交易系统的阶段&/p&&p&我曾经一个问题思考长达一个月，查资料、看书、思考，实际上任何一个看似复杂的问题只要你天天想，总有想明白的一天，只是大多数人不愿意这样做罢了。只要坚持，你解决问题的能力和洞察力都会大幅度提升。出了问题你会直觉的就找到大概的方向，过程中你养成的思维方式会带着你，你不大容易误入歧途。&/p&&p&我常常飞奔回电脑前做测试，因为闪现了灵感。即使不方便也要将闪现的东西记在随身携带的小本上。有时通宵达旦的编程，只是希望尽快的验证灵感是否有实盘的价值。&/p&&p&我想我是幸福的，幸福来自于思考的乐趣&/p&&p&幸福真的不是赚多少钱，搞一些奢侈的玩意给不相关的人看。&/p&&p&哦，对了，散步、骑车和阅读是很好的促进思考的催化剂&/p&
我以前回答过类似的问题，可参考其实把你的问题浓缩下，你是在问研究方向的问题 但却不知道MACD，RSI，KDJ…到底哪种适用，道氏，波浪，江恩…
&img src=&/50/v2-ae32e0a4e58d10efa4c42673acf2c390_b.png& data-rawwidth=&1920& data-rawheight=&937& class=&origin_image zh-lightbox-thumb& width=&1920& data-original=&/50/v2-ae32e0a4e58d10efa4c42673acf2c390_r.png&&&p&本文将会讲述Python 3.5之后出现的async/await的使用方法，以及它们的一些使用目的，如果错误，欢迎指正。&/p&&p&昨天看到David Beazley在16年的一个演讲：&a href=&/?target=https%3A///watch%3Fv%3DE-1Y4kSsAFc& class=& wrap external& target=&_blank& rel=&nofollow noreferrer&&Fear and Awaiting in Async&i class=&icon-external&&&/i&&/a&，给了我不少的感悟和启发，于是想梳理下自己的思路，所以有了以下这篇文章。&/p&&p&Python在3.5版本中引入了关于协程的语法糖async和await，关于协程的概念可以先看我在&a href=&/p/& class=&internal&&上一篇文章&/a&提到的内容。&/p&&p&看下Python中常见的几种函数形式：&/p&&p&
1. 普通函数&br&&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&function&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&mi&&1&/span&
&/code&&/pre&&/div&
2. 生成器函数&br&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&generator&/span&&span class=&p&&():&/span&
&span class=&k&&yield&/span& &span class=&mi&&1&/span&
&/code&&/pre&&/div&&p&在3.5过后，我们可以使用async修饰将普通函数和生成器函数包装成异步函数和异步生成器。&/p&&p&
3. 异步函数（协程）&/p&&br&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&async_function&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&mi&&1&/span&
&/code&&/pre&&/div&&p&
4. 异步生成器&/p&&br&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&async_generator&/span&&span class=&p&&():&/span&
&span class=&k&&yield&/span& &span class=&mi&&1&/span&
&/code&&/pre&&/div&&p&通过类型判断可以验证函数的类型&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&kn&&import&/span& &span class=&nn&&types&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&nb&&type&/span&&span class=&p&&(&/span&&span class=&n&&function&/span&&span class=&p&&)&/span& &span class=&ow&&is&/span& &span class=&n&&types&/span&&span class=&o&&.&/span&&span class=&n&&FunctionType&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&nb&&type&/span&&span class=&p&&(&/span&&span class=&n&&generator&/span&&span class=&p&&())&/span& &span class=&ow&&is&/span& &span class=&n&&types&/span&&span class=&o&&.&/span&&span class=&n&&GeneratorType&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&nb&&type&/span&&span class=&p&&(&/span&&span class=&n&&async_function&/span&&span class=&p&&())&/span& &span class=&ow&&is&/span& &span class=&n&&types&/span&&span class=&o&&.&/span&&span class=&n&&CoroutineType&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&nb&&type&/span&&span class=&p&&(&/span&&span class=&n&&async_generator&/span&&span class=&p&&())&/span& &span class=&ow&&is&/span& &span class=&n&&types&/span&&span class=&o&&.&/span&&span class=&n&&AsyncGeneratorType&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&直接调用异步函数不会返回结果，而是返回一个coroutine对象：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&async_function&/span&&span class=&p&&())&/span&
&span class=&c1&&# &coroutine object async_function at 0x102ff67d8&&/span&
&/code&&/pre&&/div&&p&协程需要通过其他方式来驱动，因此可以使用这个协程对象的send方法给协程发送一个值：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&async_function&/span&&span class=&p&&()&/span&&span class=&o&&.&/span&&span class=&n&&send&/span&&span class=&p&&(&/span&&span class=&bp&&None&/span&&span class=&p&&))&/span&
&/code&&/pre&&/div&&p&不幸的是，如果通过上面的调用会抛出一个异常：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&ne&&StopIteration&/span&&span class=&p&&:&/span& &span class=&mi&&1&/span&
&/code&&/pre&&/div&&p&因为生成器/协程在正常返回退出时会抛出一个StopIteration异常，而原来的返回值会存放在StopIteration对象的value属性中，通过以下捕获可以获取协程真正的返回值：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&try&/span&&span class=&p&&:&/span&
&span class=&n&&async_function&/span&&span class=&p&&()&/span&&span class=&o&&.&/span&&span class=&n&&send&/span&&span class=&p&&(&/span&&span class=&bp&&None&/span&&span class=&p&&)&/span&
&span class=&k&&except&/span& &span class=&ne&&StopIteration&/span& &span class=&k&&as&/span& &span class=&n&&e&/span&&span class=&p&&:&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&e&/span&&span class=&o&&.&/span&&span class=&n&&value&/span&&span class=&p&&)&/span&
&span class=&c1&&# 1&/span&
&/code&&/pre&&/div&&p&通过上面的方式来新建一个run函数来驱动协程函数：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&run&/span&&span class=&p&&(&/span&&span class=&n&&coroutine&/span&&span class=&p&&):&/span&
&span class=&k&&try&/span&&span class=&p&&:&/span&
&span class=&n&&coroutine&/span&&span class=&o&&.&/span&&span class=&n&&send&/span&&span class=&p&&(&/span&&span class=&bp&&None&/span&&span class=&p&&)&/span&
&span class=&k&&except&/span& &span class=&ne&&StopIteration&/span& &span class=&k&&as&/span& &span class=&n&&e&/span&&span class=&p&&:&/span&
&span class=&k&&return&/span& &span class=&n&&e&/span&&span class=&o&&.&/span&&span class=&n&&value&/span&
&/code&&/pre&&/div&&p&在协程函数中，可以通过await语法来挂起自身的协程，并等待另一个协程完成直到返回结果：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&async_function&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&mi&&1&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&await_coroutine&/span&&span class=&p&&():&/span&
&span class=&n&&result&/span& &span class=&o&&=&/span& &span class=&n&&await&/span& &span class=&n&&async_function&/span&&span class=&p&&()&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&result&/span&&span class=&p&&)&/span&
&span class=&n&&run&/span&&span class=&p&&(&/span&&span class=&n&&await_coroutine&/span&&span class=&p&&())&/span&
&span class=&c1&&# 1&/span&
&/code&&/pre&&/div&&p&要注意的是，await语法只能出现在通过async修饰的函数中，否则会报SyntaxError错误。&/p&&p&而且await后面的对象需要是一个Awaitable，或者实现了相关的协议。&/p&&p&查看Awaitable抽象类的代码，表明了只要一个类实现了__await__方法，那么通过它构造出来的实例就是一个Awaitable：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&Awaitable&/span&&span class=&p&&(&/span&&span class=&n&&metaclass&/span&&span class=&o&&=&/span&&span class=&n&&ABCMeta&/span&&span class=&p&&):&/span&
&span class=&n&&__slots__&/span& &span class=&o&&=&/span& &span class=&p&&()&/span&
&span class=&nd&&@abstractmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&__await__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&k&&yield&/span&
&span class=&nd&&@classmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&__subclasshook__&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&,&/span& &span class=&n&&C&/span&&span class=&p&&):&/span&
&span class=&k&&if&/span& &span class=&n&&cls&/span& &span class=&ow&&is&/span& &span class=&n&&Awaitable&/span&&span class=&p&&:&/span&
&span class=&k&&return&/span& &span class=&n&&_check_methods&/span&&span class=&p&&(&/span&&span class=&n&&C&/span&&span class=&p&&,&/span& &span class=&s2&&&__await__&&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&bp&&NotImplemented&/span&
&/code&&/pre&&/div&&p&而且可以看到，Coroutine类也继承了Awaitable，而且实现了send，throw和close方法。所以await一个调用异步函数返回的协程对象是合法的。&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&Coroutine&/span&&span class=&p&&(&/span&&span class=&n&&Awaitable&/span&&span class=&p&&):&/span&
&span class=&n&&__slots__&/span& &span class=&o&&=&/span& &span class=&p&&()&/span&
&span class=&nd&&@abstractmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&send&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&value&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&nd&&@abstractmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&throw&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&typ&/span&&span class=&p&&,&/span& &span class=&n&&val&/span&&span class=&o&&=&/span&&span class=&bp&&None&/span&&span class=&p&&,&/span& &span class=&n&&tb&/span&&span class=&o&&=&/span&&span class=&bp&&None&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&k&&def&/span& &span class=&nf&&close&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&nd&&@classmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&__subclasshook__&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&,&/span& &span class=&n&&C&/span&&span class=&p&&):&/span&
&span class=&k&&if&/span& &span class=&n&&cls&/span& &span class=&ow&&is&/span& &span class=&n&&Coroutine&/span&&span class=&p&&:&/span&
&span class=&k&&return&/span& &span class=&n&&_check_methods&/span&&span class=&p&&(&/span&&span class=&n&&C&/span&&span class=&p&&,&/span& &span class=&s1&&'__await__'&/span&&span class=&p&&,&/span& &span class=&s1&&'send'&/span&&span class=&p&&,&/span& &span class=&s1&&'throw'&/span&&span class=&p&&,&/span& &span class=&s1&&'close'&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&bp&&NotImplemented&/span&
&/code&&/pre&&/div&&p&接下来是异步生成器，来看一个例子：&/p&&p&假如我要到一家超市去购买土豆，而超市货架上的土豆数量是有限的：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&Potato&/span&&span class=&p&&:&/span&
&span class=&nd&&@classmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&make&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&,&/span& &span class=&n&&num&/span&&span class=&p&&,&/span& &span class=&o&&*&/span&&span class=&n&&args&/span&&span class=&p&&,&/span& &span class=&o&&**&/span&&span class=&n&&kws&/span&&span class=&p&&):&/span&
&span class=&n&&potatos&/span& &span class=&o&&=&/span& &span class=&p&&[]&/span&
&span class=&k&&for&/span& &span class=&n&&i&/span& &span class=&ow&&in&/span& &span class=&nb&&range&/span&&span class=&p&&(&/span&&span class=&n&&num&/span&&span class=&p&&):&/span&
&span class=&n&&potatos&/span&&span class=&o&&.&/span&&span class=&n&&append&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&o&&.&/span&&span class=&n&&__new__&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&,&/span& &span class=&o&&*&/span&&span class=&n&&args&/span&&span class=&p&&,&/span& &span class=&o&&**&/span&&span class=&n&&kws&/span&&span class=&p&&))&/span&
&span class=&k&&return&/span& &span class=&n&&potatos&/span&
&span class=&n&&all_potatos&/span& &span class=&o&&=&/span& &span class=&n&&Potato&/span&&span class=&o&&.&/span&&span class=&n&&make&/span&&span class=&p&&(&/span&&span class=&mi&&5&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&现在我想要买50个土豆，每次从货架上拿走一个土豆放到篮子：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&take_potatos&/span&&span class=&p&&(&/span&&span class=&n&&num&/span&&span class=&p&&):&/span&
&span class=&n&&count&/span& &span class=&o&&=&/span& &span class=&mi&&0&/span&
&span class=&k&&while&/span& &span class=&bp&&True&/span&&span class=&p&&:&/span&
&span class=&k&&if&/span& &span class=&nb&&len&/span&&span class=&p&&(&/span&&span class=&n&&all_potatos&/span&&span class=&p&&)&/span& &span class=&o&&==&/span& &span class=&mi&&0&/span&&span class=&p&&:&/span&
&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&o&&.&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&else&/span&&span class=&p&&:&/span&
&span class=&n&&potato&/span& &span class=&o&&=&/span& &span class=&n&&all_potatos&/span&&span class=&o&&.&/span&&span class=&n&&pop&/span&&span class=&p&&()&/span&
&span class=&k&&yield&/span& &span class=&n&&potato&/span&
&span class=&n&&count&/span& &span class=&o&&+=&/span& &span class=&mi&&1&/span&
&span class=&k&&if&/span& &span class=&n&&count&/span& &span class=&o&&==&/span& &span class=&n&&num&/span&&span class=&p&&:&/span&
&span class=&k&&break&/span&
&span class=&k&&def&/span& &span class=&nf&&buy_potatos&/span&&span class=&p&&():&/span&
&span class=&n&&bucket&/span& &span class=&o&&=&/span& &span class=&p&&[]&/span&
&span class=&k&&for&/span& &span class=&n&&p&/span& &span class=&ow&&in&/span& &span class=&n&&take_potatos&/span&&span class=&p&&(&/span&&span class=&mi&&50&/span&&span class=&p&&):&/span&
&span class=&n&&bucket&/span&&span class=&o&&.&/span&&span class=&n&&append&/span&&span class=&p&&(&/span&&span class=&n&&p&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&对应到代码中，就是迭代一个生成器的模型，显然，当货架上的土豆不够的时候，这时只能够死等，而且在上面例子中等多长时间都不会有结果（因为一切都是同步的），也许可以用多进程和多线程解决，而在现实生活中，更应该像是这样的：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&take_potatos&/span&&span class=&p&&(&/span&&span class=&n&&num&/span&&span class=&p&&):&/span&
&span class=&n&&count&/span& &span class=&o&&=&/span& &span class=&mi&&0&/span&
&span class=&k&&while&/span& &span class=&bp&&True&/span&&span class=&p&&:&/span&
&span class=&k&&if&/span& &span class=&nb&&len&/span&&span class=&p&&(&/span&&span class=&n&&all_potatos&/span&&span class=&p&&)&/span& &span class=&o&&==&/span& &span class=&mi&&0&/span&&span class=&p&&:&/span&
&span class=&n&&await&/span& &span class=&n&&ask_for_potato&/span&&span class=&p&&()&/span&
&span class=&n&&potato&/span& &span class=&o&&=&/span& &span class=&n&&all_potatos&/span&&span class=&o&&.&/span&&span class=&n&&pop&/span&&span class=&p&&()&/span&
&span class=&k&&yield&/span& &span class=&n&&potato&/span&
&span class=&n&&count&/span& &span class=&o&&+=&/span& &span class=&mi&&1&/span&
&span class=&k&&if&/span& &span class=&n&&count&/span& &span class=&o&&==&/span& &span class=&n&&num&/span&&span class=&p&&:&/span&
&span class=&k&&break&/span&
&/code&&/pre&&/div&&p&当货架上的土豆没有了之后，我可以询问超市请求需要更多的土豆，这时候需要等待一段时间直到生产者完成生产的过程：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&ask_for_potato&/span&&span class=&p&&():&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&n&&random&/span&&span class=&o&&.&/span&&span class=&n&&random&/span&&span class=&p&&())&/span&
&span class=&n&&all_potatos&/span&&span class=&o&&.&/span&&span class=&n&&extend&/span&&span class=&p&&(&/span&&span class=&n&&Potato&/span&&span class=&o&&.&/span&&span class=&n&&make&/span&&span class=&p&&(&/span&&span class=&n&&random&/span&&span class=&o&&.&/span&&span class=&n&&randint&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&,&/span& &span class=&mi&&10&/span&&span class=&p&&)))&/span&
&/code&&/pre&&/div&&p&当生产者完成和返回之后，这是便能从await挂起的地方继续往下跑，完成消费的过程。而这整一个过程，就是一个异步生成器迭代的流程：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&buy_potatos&/span&&span class=&p&&():&/span&
&span class=&n&&bucket&/span& &span class=&o&&=&/span& &span class=&p&&[]&/span&
&span class=&n&&async&/span& &span class=&k&&for&/span& &span class=&n&&p&/span& &span class=&ow&&in&/span& &span class=&n&&take_potatos&/span&&span class=&p&&(&/span&&span class=&mi&&50&/span&&span class=&p&&):&/span&
&span class=&n&&bucket&/span&&span class=&o&&.&/span&&span class=&n&&append&/span&&span class=&p&&(&/span&&span class=&n&&p&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&f&/span&&span class=&s1&&'Got potato {id(p)}...'&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&async for语法表示我们要后面迭代的是一个异步生成器。&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&main&/span&&span class=&p&&():&/span&
&span class=&kn&&import&/span& &span class=&nn&&asyncio&/span&
&span class=&n&&loop&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&get_event_loop&/span&&span class=&p&&()&/span&
&span class=&n&&res&/span& &span class=&o&&=&/span& &span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&run_until_complete&/span&&span class=&p&&(&/span&&span class=&n&&buy_potatos&/span&&span class=&p&&())&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&close&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&用asyncio运行这段代码，结果是这样的：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&o&&...&/span&
&/code&&/pre&&/div&&p&既然是异步的，在请求之后不一定要死等，而是可以做其他事情。比如除了土豆，我还想买番茄，这时只需要在事件循环中再添加一个过程：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&main&/span&&span class=&p&&():&/span&
&span class=&kn&&import&/span& &span class=&nn&&asyncio&/span&
&span class=&n&&loop&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&get_event_loop&/span&&span class=&p&&()&/span&
&span class=&n&&res&/span& &span class=&o&&=&/span& &span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&run_until_complete&/span&&span class=&p&&(&/span&&span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&wait&/span&&span class=&p&&([&/span&&span class=&n&&buy_potatos&/span&&span class=&p&&(),&/span& &span class=&n&&buy_tomatos&/span&&span class=&p&&()]))&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&close&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&再来运行这段代码：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&tomato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&tomato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&tomato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&tomato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&potato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&n&&Got&/span& &span class=&n&&tomato&/span& &span class=&mf&&.&/span&&span class=&o&&..&/span&
&span class=&o&&...&/span&
&/code&&/pre&&/div&&p&看下AsyncGenerator的定义，它需要实现__aiter__和__anext__两个核心方法，以及asend，athrow，aclose方法。&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&AsyncGenerator&/span&&span class=&p&&(&/span&&span class=&n&&AsyncIterator&/span&&span class=&p&&):&/span&
&span class=&n&&__slots__&/span& &span class=&o&&=&/span& &span class=&p&&()&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__anext__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&nd&&@abstractmethod&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&asend&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&value&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&nd&&@abstractmethod&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&athrow&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&typ&/span&&span class=&p&&,&/span& &span class=&n&&val&/span&&span class=&o&&=&/span&&span class=&bp&&None&/span&&span class=&p&&,&/span& &span class=&n&&tb&/span&&span class=&o&&=&/span&&span class=&bp&&None&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&aclose&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&nd&&@classmethod&/span&
&span class=&k&&def&/span& &span class=&nf&&__subclasshook__&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&,&/span& &span class=&n&&C&/span&&span class=&p&&):&/span&
&span class=&k&&if&/span& &span class=&n&&cls&/span& &span class=&ow&&is&/span& &span class=&n&&AsyncGenerator&/span&&span class=&p&&:&/span&
&span class=&k&&return&/span& &span class=&n&&_check_methods&/span&&span class=&p&&(&/span&&span class=&n&&C&/span&&span class=&p&&,&/span& &span class=&s1&&'__aiter__'&/span&&span class=&p&&,&/span& &span class=&s1&&'__anext__'&/span&&span class=&p&&,&/span&
&span class=&s1&&'asend'&/span&&span class=&p&&,&/span& &span class=&s1&&'athrow'&/span&&span class=&p&&,&/span& &span class=&s1&&'aclose'&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&bp&&NotImplemented&/span&
&/code&&/pre&&/div&&p&异步生成器是在3.6之后才有的特性，同样的还有异步推导表达式，因此在上面的例子中，也可以写成这样：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&bucket&/span& &span class=&o&&=&/span& &span class=&p&&[&/span&&span class=&n&&p&/span& &span class=&n&&async&/span& &span class=&k&&for&/span& &span class=&n&&p&/span& &span class=&ow&&in&/span& &span class=&n&&take_potatos&/span&&span class=&p&&(&/span&&span class=&mi&&50&/span&&span class=&p&&)]&/span&
&/code&&/pre&&/div&&p&类似的，还有await表达式：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&result&/span& &span class=&o&&=&/span& &span class=&p&&[&/span&&span class=&n&&await&/span& &span class=&n&&fun&/span&&span class=&p&&()&/span& &span class=&k&&for&/span& &span class=&n&&fun&/span& &span class=&ow&&in&/span& &span class=&n&&funcs&/span& &span class=&k&&if&/span& &span class=&n&&await&/span& &span class=&n&&condition&/span&&span class=&p&&()]&/span&
&/code&&/pre&&/div&&p&除了函数之外，类实例的普通方法也能用async语法修饰：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&ThreeTwoOne&/span&&span class=&p&&:&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&begin&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&3&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&2&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&game&/span&&span class=&p&&():&/span&
&span class=&n&&t&/span& &span class=&o&&=&/span& &span class=&n&&ThreeTwoOne&/span&&span class=&p&&()&/span&
&span class=&n&&await&/span& &span class=&n&&t&/span&&span class=&o&&.&/span&&span class=&n&&begin&/span&&span class=&p&&()&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'start'&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&实例方法的调用同样是返回一个coroutine：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&function&/span& &span class=&o&&=&/span& &span class=&n&&ThreeTwoOne&/span&&span class=&o&&.&/span&&span class=&n&&begin&/span&
&span class=&n&&method&/span& &span class=&o&&=&/span& &span class=&n&&function&/span&&span class=&o&&.&/span&&span class=&n&&__get__&/span&&span class=&p&&(&/span&&span class=&n&&ThreeTwoOne&/span&&span class=&p&&,&/span& &span class=&n&&ThreeTwoOne&/span&&span class=&p&&())&/span&
&span class=&kn&&import&/span& &span class=&nn&&inspect&/span&
&span class=&k&&assert&/span& &span class=&n&&inspect&/span&&span class=&o&&.&/span&&span class=&n&&isfunction&/span&&span class=&p&&(&/span&&span class=&n&&function&/span&&span class=&p&&)&/span&
&span class=&k&&assert&/span& &span class=&n&&inspect&/span&&span class=&o&&.&/span&&span class=&n&&ismethod&/span&&span class=&p&&(&/span&&span class=&n&&method&/span&&span class=&p&&)&/span&
&span class=&k&&assert&/span& &span class=&n&&inspect&/span&&span class=&o&&.&/span&&span class=&n&&iscoroutine&/span&&span class=&p&&(&/span&&span class=&n&&method&/span&&span class=&p&&())&/span&
&/code&&/pre&&/div&&p&同理还有类方法：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&ThreeTwoOne&/span&&span class=&p&&:&/span&
&span class=&nd&&@classmethod&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&begin&/span&&span class=&p&&(&/span&&span class=&n&&cls&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&3&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&2&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&game&/span&&span class=&p&&():&/span&
&span class=&n&&await&/span& &span class=&n&&ThreeTwoOne&/span&&span class=&o&&.&/span&&span class=&n&&begin&/span&&span class=&p&&()&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'start'&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&根据PEP 492中，async也可以应用到上下文管理器中，__aenter__和__aexit__需要返回一个Awaitable：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&GameContext&/span&&span class=&p&&:&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__aenter__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game loading...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__aexit__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&exc_type&/span&&span class=&p&&,&/span& &span class=&n&&exc&/span&&span class=&p&&,&/span& &span class=&n&&tb&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game exit...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&game&/span&&span class=&p&&():&/span&
&span class=&n&&async&/span& &span class=&k&&with&/span& &span class=&n&&GameContext&/span&&span class=&p&&():&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game start...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&2&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&在3.7版本，contextlib中会新增一个asynccontextmanager装饰器来包装一个实现异步协议的上下文管理器：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&kn&&from&/span& &span class=&nn&&contextlib&/span& &span class=&kn&&import&/span& &span class=&n&&asynccontextmanager&/span&
&span class=&nd&&@asynccontextmanager&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&get_connection&/span&&span class=&p&&():&/span&
&span class=&n&&conn&/span& &span class=&o&&=&/span& &span class=&n&&await&/span& &span class=&n&&acquire_db_connection&/span&&span class=&p&&()&/span&
&span class=&k&&try&/span&&span class=&p&&:&/span&
&span class=&k&&yield&/span&
&span class=&k&&finally&/span&&span class=&p&&:&/span&
&span class=&n&&await&/span& &span class=&n&&release_db_connection&/span&&span class=&p&&(&/span&&span class=&n&&conn&/span&&span class=&p&&)&/span&
&/code&&/pre&&/div&&p&async修饰符也能用在__call__方法上：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&GameContext&/span&&span class=&p&&:&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__aenter__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_started&/span& &span class=&o&&=&/span& &span class=&n&&time&/span&&span class=&p&&()&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game loading...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&bp&&self&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__aexit__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&exc_type&/span&&span class=&p&&,&/span& &span class=&n&&exc&/span&&span class=&p&&,&/span& &span class=&n&&tb&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game exit...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&__call__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&o&&*&/span&&span class=&n&&args&/span&&span class=&p&&,&/span& &span class=&o&&**&/span&&span class=&n&&kws&/span&&span class=&p&&):&/span&
&span class=&k&&if&/span& &span class=&n&&args&/span&&span class=&p&&[&/span&&span class=&mi&&0&/span&&span class=&p&&]&/span& &span class=&o&&==&/span& &span class=&s1&&'time'&/span&&span class=&p&&:&/span&
&span class=&k&&return&/span& &span class=&n&&time&/span&&span class=&p&&()&/span& &span class=&o&&-&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_started&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&game&/span&&span class=&p&&():&/span&
&span class=&n&&async&/span& &span class=&k&&with&/span& &span class=&n&&GameContext&/span&&span class=&p&&()&/span& &span class=&k&&as&/span& &span class=&n&&ctx&/span&&span class=&p&&:&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game start...'&/span&&span class=&p&&)&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&2&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s1&&'game time: '&/span&&span class=&p&&,&/span& &span class=&n&&await&/span& &span class=&n&&ctx&/span&&span class=&p&&(&/span&&span class=&s1&&'time'&/span&&span class=&p&&))&/span&
&/code&&/pre&&/div&&p&&strong&await和yield from&/strong&&/p&&p&Python3.3的yield from语法可以把生成器的操作委托给另一个生成器，生成器的调用方可以直接与子生成器进行通信：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&sub_gen&/span&&span class=&p&&():&/span&
&span class=&k&&yield&/span& &span class=&mi&&1&/span&
&span class=&k&&yield&/span& &span class=&mi&&2&/span&
&span class=&k&&yield&/span& &span class=&mi&&3&/span&
&span class=&k&&def&/span& &span class=&nf&&gen&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&p&&(&/span&&span class=&k&&yield from&/span& &span class=&n&&sub_gen&/span&&span class=&p&&())&/span&
&span class=&k&&def&/span& &span class=&nf&&main&/span&&span class=&p&&():&/span&
&span class=&k&&for&/span& &span class=&n&&val&/span& &span class=&ow&&in&/span& &span class=&n&&gen&/span&&span class=&p&&():&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&val&/span&&span class=&p&&)&/span&
&span class=&c1&&# 1&/span&
&span class=&c1&&# 2&/span&
&span class=&c1&&# 3&/span&
&/code&&/pre&&/div&&p&利用这一特性，使用yield from能够编写出类似协程效果的函数调用，在3.5之前，asyncio正是使用@asyncio.coroutine和yield from语法来创建协程：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&c1&&# https://docs.python.org/3.4/library/asyncio-task.html&/span&
&span class=&kn&&import&/span& &span class=&nn&&asyncio&/span&
&span class=&nd&&@asyncio.coroutine&/span&
&span class=&k&&def&/span& &span class=&nf&&compute&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s2&&&Compute &/span&&span class=&si&&%s&/span&&span class=&s2&& + &/span&&span class=&si&&%s&/span&&span class=&s2&& ...&&/span& &span class=&o&&%&/span& &span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&))&/span&
&span class=&k&&yield from&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mf&&1.0&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&n&&x&/span& &span class=&o&&+&/span& &span class=&n&&y&/span&
&span class=&nd&&@asyncio.coroutine&/span&
&span class=&k&&def&/span& &span class=&nf&&print_sum&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&):&/span&
&span class=&n&&result&/span& &span class=&o&&=&/span& &span class=&k&&yield from&/span& &span class=&n&&compute&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s2&&&&/span&&span class=&si&&%s&/span&&span class=&s2&& + &/span&&span class=&si&&%s&/span&&span class=&s2&& = &/span&&span class=&si&&%s&/span&&span class=&s2&&&&/span& &span class=&o&&%&/span& &span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&,&/span& &span class=&n&&result&/span&&span class=&p&&))&/span&
&span class=&n&&loop&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&get_event_loop&/span&&span class=&p&&()&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&run_until_complete&/span&&span class=&p&&(&/span&&span class=&n&&print_sum&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&,&/span& &span class=&mi&&2&/span&&span class=&p&&))&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&close&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&然而，用yield from容易在表示协程和生成器中混淆，没有良好的语义性，所以在Python 3.5推出了更新的async/await表达式来作为协程的语法。&/p&&p&因此类似以下的调用是等价的：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&n&&async&/span& &span class=&k&&with&/span& &span class=&n&&lock&/span&&span class=&p&&:&/span&
&span class=&o&&...&/span&
&span class=&k&&with&/span& &span class=&p&&(&/span&&span class=&k&&yield from&/span& &span class=&n&&lock&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&c1&&######################&/span&
&span class=&k&&def&/span& &span class=&nf&&main&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&p&&(&/span&&span class=&k&&yield from&/span& &span class=&n&&coro&/span&&span class=&p&&())&/span&
&span class=&k&&def&/span& &span class=&nf&&main&/span&&span class=&p&&():&/span&
&span class=&k&&return&/span& &span class=&p&&(&/span&&span class=&n&&await&/span& &span class=&n&&coro&/span&&span class=&p&&())&/span&
&/code&&/pre&&/div&&p&那么，怎么把生成器包装为一个协程对象呢？这时候可以用到types包中的coroutine装饰器（如果使用asyncio做驱动的话，那么也可以使用asyncio的coroutine装饰器），@types.coroutine装饰器会将一个生成器函数包装为协程对象：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&kn&&import&/span& &span class=&nn&&asyncio&/span&
&span class=&kn&&import&/span& &span class=&nn&&types&/span&
&span class=&nd&&@types.coroutine&/span&
&span class=&k&&def&/span& &span class=&nf&&compute&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&):&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s2&&&Compute &/span&&span class=&si&&%s&/span&&span class=&s2&& + &/span&&span class=&si&&%s&/span&&span class=&s2&& ...&&/span& &span class=&o&&%&/span& &span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&))&/span&
&span class=&k&&yield from&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mf&&1.0&/span&&span class=&p&&)&/span&
&span class=&k&&return&/span& &span class=&n&&x&/span& &span class=&o&&+&/span& &span class=&n&&y&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&print_sum&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&):&/span&
&span class=&n&&result&/span& &span class=&o&&=&/span& &span class=&n&&await&/span& &span class=&n&&compute&/span&&span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&)&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&s2&&&&/span&&span class=&si&&%s&/span&&span class=&s2&& + &/span&&span class=&si&&%s&/span&&span class=&s2&& = &/span&&span class=&si&&%s&/span&&span class=&s2&&&&/span& &span class=&o&&%&/span& &span class=&p&&(&/span&&span class=&n&&x&/span&&span class=&p&&,&/span& &span class=&n&&y&/span&&span class=&p&&,&/span& &span class=&n&&result&/span&&span class=&p&&))&/span&
&span class=&n&&loop&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&get_event_loop&/span&&span class=&p&&()&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&run_until_complete&/span&&span class=&p&&(&/span&&span class=&n&&print_sum&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&,&/span& &span class=&mi&&2&/span&&span class=&p&&))&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&close&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&尽管两个函数分别使用了新旧语法，但他们都是协程对象，也分别称作&em&native coroutine&/em&以及&em&generator-based coroutine&/em&，因此不用担心语法问题。&/p&&p&下面观察一个asyncio中Future的例子：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&kn&&import&/span& &span class=&nn&&asyncio&/span&
&span class=&n&&future&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&Future&/span&&span class=&p&&()&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&coro1&/span&&span class=&p&&():&/span&
&span class=&n&&await&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&sleep&/span&&span class=&p&&(&/span&&span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&future&/span&&span class=&o&&.&/span&&span class=&n&&set_result&/span&&span class=&p&&(&/span&&span class=&s1&&'data'&/span&&span class=&p&&)&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&coro2&/span&&span class=&p&&():&/span&
&span class=&k&&print&/span&&span class=&p&&(&/span&&span class=&n&&await&/span& &span class=&n&&future&/span&&span class=&p&&)&/span&
&span class=&n&&loop&/span& &span class=&o&&=&/span& &span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&get_event_loop&/span&&span class=&p&&()&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&run_until_complete&/span&&span class=&p&&(&/span&&span class=&n&&asyncio&/span&&span class=&o&&.&/span&&span class=&n&&wait&/span&&span class=&p&&([&/span&
&span class=&n&&coro1&/span&&span class=&p&&(),&/span&
&span class=&n&&coro2&/span&&span class=&p&&()&/span&
&span class=&p&&]))&/span&
&span class=&n&&loop&/span&&span class=&o&&.&/span&&span class=&n&&close&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&两个协程在在事件循环中，协程coro1在执行第一句后挂起自身切到asyncio.sleep，而协程coro2一直等待future的结果，让出事件循环，计时器结束后coro1执行了第二句设置了future的值，被挂起的coro2恢复执行，打印出future的结果'data'。&/p&&p&future可以被await证明了future对象是一个Awaitable，进入Future类的源码可以看到有一段代码显示了future实现了__await__协议：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&Future&/span&&span class=&p&&:&/span&
&span class=&o&&...&/span&
&span class=&k&&def&/span& &span class=&nf&&__iter__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&k&&if&/span& &span class=&ow&&not&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&done&/span&&span class=&p&&():&/span&
&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_asyncio_future_blocking&/span& &span class=&o&&=&/span& &span class=&bp&&True&/span&
&span class=&k&&yield&/span& &span class=&bp&&self&/span&
&span class=&c1&&# This tells Task to wait for completion.&/span&
&span class=&k&&assert&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&done&/span&&span class=&p&&(),&/span& &span class=&s2&&&yield from wasn't used with future&&/span&
&span class=&k&&return&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&result&/span&&span class=&p&&()&/span&
&span class=&c1&&# May raise too.&/span&
&span class=&k&&if&/span& &span class=&n&&compat&/span&&span class=&o&&.&/span&&span class=&n&&PY35&/span&&span class=&p&&:&/span&
&span class=&n&&__await__&/span& &span class=&o&&=&/span& &span class=&n&&__iter__&/span& &span class=&c1&&# make compatible with 'await' expression&/span&
&/code&&/pre&&/div&&p&当执行&strong&await future&/strong&这行代码时，future中的这段代码就会被执行，首先future检查它自身是否已经完成，如果没有完成，挂起自身，告知当前的Task（任务）等待future完成。&/p&&p&当future执行set_result方法时，会触发以下的代码，设置结果，标记future已经完成：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&def&/span& &span class=&nf&&set_result&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&,&/span& &span class=&n&&result&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&k&&if&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_state&/span& &span class=&o&&!=&/span& &span class=&n&&_PENDING&/span&&span class=&p&&:&/span&
&span class=&k&&raise&/span& &span class=&n&&InvalidStateError&/span&&span class=&p&&(&/span&&span class=&s1&&'{}: {!r}'&/span&&span class=&o&&.&/span&&span class=&n&&format&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_state&/span&&span class=&p&&,&/span& &span class=&bp&&self&/span&&span class=&p&&))&/span&
&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_result&/span& &span class=&o&&=&/span& &span class=&n&&result&/span&
&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_state&/span& &span class=&o&&=&/span& &span class=&n&&_FINISHED&/span&
&span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&_schedule_callbacks&/span&&span class=&p&&()&/span&
&/code&&/pre&&/div&&p&最后future会调度自身的回调函数，触发Task._step()告知Task驱动future从之前挂起的点恢复执行，不难看出，future会执行下面的代码：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&k&&class&/span& &span class=&nc&&Future&/span&&span class=&p&&:&/span&
&span class=&o&&...&/span&
&span class=&k&&def&/span& &span class=&nf&&__iter__&/span&&span class=&p&&(&/span&&span class=&bp&&self&/span&&span class=&p&&):&/span&
&span class=&o&&...&/span&
&span class=&k&&assert&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&done&/span&&span class=&p&&(),&/span& &span class=&s2&&&yield from wasn't used with future&&/span&
&span class=&k&&return&/span& &span class=&bp&&self&/span&&span class=&o&&.&/span&&span class=&n&&result&/span&&span class=&p&&()&/span&
&span class=&c1&&# May raise too.&/span&
&/code&&/pre&&/div&&p&最终返回结果给调用方。&/p&&p&前面讲了那么多关于asyncio的例子，那么除了asyncio，就没有其他协程库了吗？asyncio作为python的标准库，自然受到很多青睐，但它有时候还是显得太重量了，尤其是提供了许多复杂的轮子和协议，不便于使用。&/p&&p&你可以理解为，asyncio是使用async/await语法开发的协程库，而不是有asyncio才能用async/await，除了asyncio之外，curio和trio是更加轻量级的替代物，而且也更容易使用。&/p&&p&curio的作者是David Beazley，下面是使用curio创建tcp server的例子，据说这是dabeaz理想中的一个异步服务器的样子：&/p&&div class=&highlight&&&pre&&code class=&language-python&&&span&&/span&&span class=&kn&&from&/span& &span class=&nn&&curio&/span& &span class=&kn&&import&/span& &span class=&n&&run&/span&&span class=&p&&,&/span& &span class=&n&&spawn&/span&
&span class=&kn&&from&/span& &span class=&nn&&curio.socket&/span& &span class=&kn&&import&/span& &span class=&o&&*&/span&
&span class=&n&&async&/span& &span class=&k&&def&/span& &span class=&nf&&echo_server&/span&&span class=&p&&(&/span&&span class=&n&&address&/span&&span class=&p&&):&/span&
&span class=&n&&sock&/span& &span class=&o&&=&/span& &span class=&n&&socket&/span&&span class=&p&&(&/span&&span class=&n&&AF_INET&/span&&span class=&p&&,&/span& &span class=&n&&SOCK_STREAM&/span&&span class=&p&&)&/span&
&span class=&n&&sock&/span&&span class=&o&&.&/span&&span class=&n&&setsockopt&/span&&span class=&p&&(&/span&&span class=&n&&SOL_SOCKET&/span&&span class=&p&&,&/span& &span class=&n&&SO_REUSEADDR&/span&&span class=&p&&,&/span& &span class=&mi&&1&/span&&span class=&p&&)&/span&
&span class=&n&&sock&/span&&span class=&o&&.&/span&&span class=&n&&bind&/span&&span class=&p&&(&/span&&span class=&n&&address&/span&&span class=&p&&}