讯享网

                <span id="Label3"><p>http://www.cnblogs.com/wupeiqi/articles/4938499.html</p><p>&nbsp;</p><p>python<span style="font-family:‘宋体‘;">解释器执行顺序：<span style="background:#FF0000;">从上到下</span></span></p><p><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">foo(): --&gt;</span><span style="font-size:12px;font-family:‘宋体‘;">将foo函数读入内存，但不执行函数体内容</span><span style="font-size:12px;"><br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘abc‘ &nbsp;--&gt;</span></strong><strong><span style="font-size:12px;font-family:‘宋体‘;color:#008000;">略过这行</span></strong><strong><span style="font-size:12px;color:#008000;"><br /></span></strong><span style="font-size:12px;">foo &nbsp;--&gt;</span><span style="font-size:12px;font-family:‘宋体‘;">表示</span><span style="font-size:12px;">foo</span><span style="font-size:12px;font-family:‘宋体‘;">函数，</span><span style="font-size:12px;">foo</span><span style="font-size:12px;font-family:‘宋体‘;">指向函数的内存地址</span><span style="font-size:12px;"><br />foo() &nbsp;--&gt;</span><span style="font-size:12px;font-family:‘宋体‘;">表示执行</span><span style="font-size:12px;">foo</span><span style="font-size:12px;font-family:‘宋体‘;">函数，反过头取执行函数体内容</span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘abc‘</span></strong><span style="font-size:12px;"><br />foo = </span><strong><span style="font-size:12px;color:#000080;">lambda </span></strong><span style="font-size:12px;">a : a + </span><span style="font-size:12px;color:#0000FF;">1 --&gt;foo</span><span style="font-size:12px;font-family:‘宋体‘;color:#0000FF;">指向另外一个函数的内存地址，这个函数实现的功能是</span><span style="font-size:12px;color:#0000FF;">a+1</span></p><p><span style="font-size:12px;">foo()&nbsp; --&gt;</span><span style="font-size:12px;font-family:‘宋体‘;">执行</span><span style="font-size:12px;">a+1</span><span style="font-size:12px;font-family:‘宋体‘;">这个函数的函数体</span></p><p>&nbsp;</p><p><span style="font-family:‘宋体‘;">函数调用函数：</span></p><p style="background:#FFFFFF;"><strong><span style="font-size:12px;font-family:‘宋体‘;color:#000080;">def </span></strong><span style="font-size:12px;font-family:‘宋体‘;">f1(arg):<br />&nbsp;&nbsp;&nbsp; arg()<br /></span><strong><span style="font-size:12px;font-family:‘宋体‘;color:#000080;">def </span></strong><span style="font-size:12px;font-family:‘宋体‘;">func():<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;font-family:‘宋体‘;color:#000080;">print </span></strong><strong><span style="font-size:12px;font-family:‘宋体‘;color:#008000;">"func"<br /></span></strong><span style="font-size:12px;font-family:‘宋体‘;">f1(func)</span></p><p>python<span style="font-family:‘宋体‘;">解释器从上往下执行</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第一步：执行</span><span style="font-size:12px;">def f1(arg): </span><span style="font-size:12px;font-family:‘宋体‘;">将函数写入内存，但是不执行函数体的内容</span><span style="font-size:12px;">arg()</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第二步：执行</span><span style="font-size:12px;">def func():</span><span style="font-size:12px;font-family:‘宋体‘;">将函数写入内存，但是不执行函数体的内容</span><span style="font-size:12px;">print ‘func‘</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第三步：执行</span><span style="font-size:12px;">f1(func)</span><span style="font-size:12px;font-family:‘宋体‘;">调用函数</span><span style="font-size:12px;">f1</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第四步：执行</span><span style="font-size:12px;">def f1(arg): </span><span style="font-size:12px;font-family:‘宋体‘;">，这时</span><span style="font-size:12px;">arg = func</span><span style="font-size:12px;font-family:‘宋体‘;">，</span><span style="font-size:12px;">arg</span><span style="font-size:12px;font-family:‘宋体‘;">指向函数的内存地址</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第五步：执行</span><span style="font-size:12px;">arg()</span><span style="font-size:12px;font-family:‘宋体‘;">，</span><span style="font-size:12px;">arg() = func()</span><span style="font-size:12px;font-family:‘宋体‘;">，也就是执行</span><span style="font-size:12px;">func()</span><span style="font-size:12px;font-family:‘宋体‘;">函数</span><span style="font-size:12px;"> </span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第六步：执行</span><span style="font-size:12px;">def func():</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第七步：执行</span><span style="font-size:12px;">print ‘12‘</span></p><p><span style="font-size:12px;">&nbsp;</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">业务场景：</span></p><p><span style="font-family:‘宋体‘;">基础平台运维编写各种基础函数，提供各种</span>API<span style="font-family:‘宋体‘;">给产线，来查询数据库，各个机器的使用情况等功能</span></p><p><span style="font-family:‘宋体‘;">之前调用</span>API<span style="font-family:‘宋体‘;">没有做认证，现在想在</span>500<span style="font-family:‘宋体‘;">个函数中加入</span>auth()<span style="font-family:‘宋体‘;">函数做认证，基本的做法：</span></p><pre style="background-color:#FFFFFF;"><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">auth():<br />&nbsp;&nbsp;&nbsp; xxxxxx</span></pre><pre style="background-color:#FFFFFF;"><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">f1():<br />&nbsp;&nbsp;&nbsp; auth()&nbsp; --&gt;</span><span style="font-size:12px;">在函数体中增加auth()函数做认证<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">"f1"<br /></span></strong><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">f2():<br />&nbsp;&nbsp;&nbsp; auth()&nbsp; --&gt;</span><span style="font-size:12px;">在函数体中增加auth()函数做认证<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">"f2"</span></strong></pre><p><span style="font-size:12px;font-family:‘宋体‘;">但是由于开放封闭原则：</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">函数体不能被修改，只能修改配置文件或者</span><span style="font-size:12px;">main()</span><span style="font-size:12px;font-family:‘宋体‘;">函数来修改函数的执行顺序，或者增加新的函数来改变实现的功能</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">例如原来定义的函数执行顺序为</span><span style="font-size:12px;">1-&gt;2-&gt;3-&gt;4</span><span style="font-size:12px;font-family:‘宋体‘;">，现在修改为</span><span style="font-size:12px;">1-&gt;2-<span style="background:#FFFF00;">&gt;2.5-</span>&gt;4-&gt;3</span><span style="font-size:12px;font-family:‘宋体‘;">，增加了一个</span><span style="font-size:12px;">2.5</span><span style="font-size:12px;font-family:‘宋体‘;">功能，并且调换了</span><span style="font-size:12px;">3</span><span style="font-size:12px;font-family:‘宋体‘;">和</span><span style="font-size:12px;">4</span><span style="font-size:12px;font-family:‘宋体‘;">的顺序</span></p><p><span style="font-family:‘宋体‘;">因此需要这样写：</span></p><pre style="background-color:#FFFFFF;"><span style="margin-left:48px;margin-top:36px;width:31px;height:52px;"><img  alt="技术分享" onl oad="if(this.width>650) this.width=650;" width="31" height="52" src="http://www.mamicode.com/e/u261/themes/default/images/spacer.gif" style="background:url(&quot;/e/u261/themes/default/images/word.gif&quot;) no-repeat center;border:1px solid #ddd;" alt="spacer.gif" /></span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">auth(func):<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;background:#FF0000;">inner</span><span style="font-size:12px;">():<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘</span></strong><strong><span style="font-size:12px;color:#008000;">验证功能‘<br />&nbsp;&nbsp;&nbsp; </span></strong><span style="font-size:12px;">func()<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">return </span></strong><span style="font-size:12px;background:#FF0000;">inner</span><span style="font-size:12px;"><br /></span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">f1():&nbsp; --&gt;</span><span style="font-size:12px;">原函数<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘f1‘<br /></span></strong><span style="font-size:12px;">retval = auth(f1)<br />retval()</span></pre><p>&nbsp;</p><p><span style="font-size:12px;font-family:‘宋体‘;">第一步：执行def auth(func): ，将auth()函数加载到内存，但不执行函数体内容</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第二步：执行def f1(): ，将f1()函数加载到内存，但不执行函数体内容</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第三步：执行retval = auth(f1)，调用auth()函数，同时传参f1</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第四步：执行def auth(func): ，这时func == f1</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第五步：执行def inner():，将auth()函数加载到内存，但是不执行inner()函数的函数体</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第六步：执行return inner，这时retval == inner，retval也就等于整个inner()函数体</span></p><p><span style="font-size:12px;font-family:‘宋体‘;">第七步：执行retval()，retval()==inner(),也就是执行inner()函数体，inner()函数体中有func()，而func()==f1，就执行了原来的函数f1</span></p><p><span style="font-family:‘宋体‘;">如果将</span><span style="font-size:12px;">retval = auth(f1)</span><span style="font-size:12px;font-family:‘宋体‘;">，改写为</span><span style="font-size:12px;">f1= auth(f1) </span><span style="font-size:12px;font-family:‘宋体‘;">（第一个</span><span style="font-size:12px;">f1</span><span style="font-size:12px;font-family:‘宋体‘;">是新</span><span style="font-size:12px;">f1</span><span style="font-size:12px;font-family:‘宋体‘;">，第二个</span><span style="font-size:12px;">f1</span><span style="font-size:12px;font-family:‘宋体‘;">是老的</span><span style="font-size:12px;">f1</span><span style="font-size:12px;font-family:‘宋体‘;">函数）那么业务线的人就可以不用修改代码了</span></p><p><span style="font-size:12px;">python</span><span style="font-size:12px;font-family:‘宋体‘;">提供了简单的写法，这种写法就是装饰器：</span></p><pre style="background-color:#FFFFFF;"><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">auth(func):<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">inner():<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘</span></strong><strong><span style="font-size:12px;color:#008000;">认证功能‘<br />&nbsp;&nbsp;&nbsp; </span></strong><span style="font-size:12px;">func()</span></pre><pre style="background-color:#FFFFFF;"><span style="font-size:12px;">&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘</span></strong><strong><span style="font-size:12px;color:#008000;">打印日志‘</span></strong><span style="font-size:12px;"><br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">return </span></strong><span style="font-size:12px;">inner</span></pre><pre style="background-color:#FFFFFF;"><span style="margin-left:55px;margin-top:38px;width:18px;height:28px;"><img  alt="技术分享" onl oad="if(this.width>650) this.width=650;" width="18" height="28" src="http://www.mamicode.com/e/u261/themes/default/images/spacer.gif" style="background:url(&quot;/e/u261/themes/default/images/word.gif&quot;) no-repeat center;border:1px solid #ddd;" alt="spacer.gif" /></span><span style="margin-left:55px;margin-top:36px;width:33px;height:174px;"><img  alt="技术分享" onl oad="if(this.width>650) this.width=650;" width="33" height="174" src="http://www.mamicode.com/e/u261/themes/default/images/spacer.gif" style="background:url(&quot;/e/u261/themes/default/images/word.gif&quot;) no-repeat center;border:1px solid #ddd;" alt="spacer.gif" /></span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">auth_arg1(func):<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">inner(<span style="background:#FF0000;">arg</span>):<br />&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘</span></strong><strong><span style="font-size:12px;color:#008000;">认证功能‘<br />&nbsp;&nbsp;&nbsp; </span></strong><span style="font-size:12px;">func(<span style="background:#FF0000;">arg</span>)</span></pre><pre style="background-color:#FFFFFF;"><span style="font-size:12px;">&nbsp;&nbsp;&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘</span></strong><strong><span style="font-size:12px;color:#008000;">打印日志‘</span></strong><span style="font-size:12px;"><br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">return </span></strong><span style="font-size:12px;">inner<br />@</span><span style="font-size:12px;color:#0000B2;">auth&nbsp; ==</span><span style="font-size:12px;color:#0000B2;">》会执行f1 = auth(f1)，也就是inner()函数的返回值复制给f1<br /></span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">f1():<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘f1‘</span></strong></pre><pre style="background-color:#FFFFFF;"><span style="font-size:12px;">@</span><span style="font-size:12px;color:#0000B2;">auth_arg1&nbsp; ==</span><span style="font-size:12px;color:#0000B2;">》会执行f1 = auth(f1)，也就是inner()函数的返回值复制给f1<br /></span><strong><span style="font-size:12px;color:#000080;">def </span></strong><span style="font-size:12px;">f2(<span style="background:#FF0000;">arg</span>):<br />&nbsp; </span><strong><span style="font-size:12px;color:#000080;">print </span></strong><strong><span style="font-size:12px;color:#008000;">‘f2,arg‘</span></strong></pre><pre style="background-color:#FFFFFF;">装饰器的实质就是在不修改f1函数体的情况下，执行f1函数之前，执行一个auth函数</pre><pre style="background-color:#FFFFFF;">有了装饰器，基础平台给500个函数增加认证功能，在不破坏开放封闭原则的情况下，只需要写一个auth函数和500个@auth，auth函数的inner子函数中实现认证功能，业务线不需要做任何修改，实现的功能就是f1函数执行之前进行身份验证，f1功能执行之后打印日志</pre><pre style="background-color:#FFFFFF;">当函数f2有一个参数的时候，需要另外写一个有一个参数的装饰器auth_arg1，在f2之前写上@auth_arg1即可</pre><pre style="background-color:#FFFFFF;">&nbsp;<br /></pre><pre style="background-color:#FFFFFF;">第5天该看06了</pre><p><br /></p><p>python笔记day5</p></span>