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<title>[雪峰磁针石博客]python3快速入门教程1 turtle绘图-3循环</title>
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<a href="/python3_crash3.html" rel="bookmark"
title="Permalink to [雪峰磁针石博客]python3快速入门教程1 turtle绘图-3循环">[雪峰磁针石博客]python3快速入门教程1 turtle绘图-3循环</a></h1>
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<abbr class="published" title="2018-09-02T10:20:00+08:00">
Published: 日 02 九月 2018
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By <a class="url fn" href="/author/andrew.html">andrew</a>
</address>
<p>In <a href="/category/python.html">python</a>.</p>
</footer><!-- /.post-info --> <h2 id="_1">语法基础</h2>
<h3 id="for">for语句</h3>
<p>Python的for语句针对序列(列表或字符串等)中的子项进行循环，按它们在序列中的顺序来进行迭代。 </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
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8</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="c1"># Measure some strings:</span>
<span class="o">...</span> <span class="n">words</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'cat'</span><span class="p">,</span> <span class="s1">'window'</span><span class="p">,</span> <span class="s1">'defenestrate'</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">w</span> <span class="ow">in</span> <span class="n">words</span><span class="p">:</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">w</span><span class="p">,</span> <span class="nb">len</span><span class="p">(</span><span class="n">w</span><span class="p">))</span>
<span class="o">...</span>
<span class="n">cat</span> <span class="mi">3</span>
<span class="n">window</span> <span class="mi">6</span>
<span class="n">defenestrate</span> <span class="mi">12</span>
</pre></div>
</td></tr></table>
<p>在迭代过程中修改迭代序列不安全，可能导致部分元素重复两次，建议先拷贝: </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
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6</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">for</span> <span class="n">w</span> <span class="ow">in</span> <span class="n">words</span><span class="p">[:]:</span> <span class="c1"># Loop over a slice copy of the entire list.</span>
<span class="o">...</span> <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">w</span><span class="p">)</span> <span class="o">></span> <span class="mi">6</span><span class="p">:</span>
<span class="o">...</span> <span class="n">words</span><span class="o">.</span><span class="n">insert</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">w</span><span class="p">)</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="n">words</span>
<span class="p">[</span><span class="s1">'defenestrate'</span><span class="p">,</span> <span class="s1">'cat'</span><span class="p">,</span> <span class="s1">'window'</span><span class="p">,</span> <span class="s1">'defenestrate'</span><span class="p">]</span>
</pre></div>
</td></tr></table>
<h3 id="range">range()函数</h3>
<p>内置函数 range()生成等差数值序列：</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="nb">range</span><span class="p">(</span><span class="mi">10</span><span class="p">)</span>
<span class="p">[</span><span class="mi">0</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="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
</pre></div>
</td></tr></table>
<p>range(10) 生成了一个包含10个值的链表，但是不包含最右边的值。默认从0开始，也可以让range 从其他值开始，或者指定不同的增量值(甚至是负数，有时也称"步长"）:</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
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8</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="nb">range</span><span class="p">(</span><span class="mi">5</span><span class="p">,</span> <span class="mi">10</span><span class="p">)</span>
<span class="p">[</span><span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
<span class="o">>>></span> <span class="nb">range</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
<span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">9</span><span class="p">]</span>
<span class="o">>>></span> <span class="nb">range</span><span class="p">(</span><span class="o">-</span><span class="mi">10</span><span class="p">,</span> <span class="o">-</span><span class="mi">100</span><span class="p">,</span> <span class="o">-</span><span class="mi">30</span><span class="p">)</span>
<span class="p">[</span><span class="o">-</span><span class="mi">10</span><span class="p">,</span> <span class="o">-</span><span class="mi">40</span><span class="p">,</span> <span class="o">-</span><span class="mi">70</span><span class="p">]</span>
<span class="o">>>></span> <span class="nb">range</span><span class="p">(</span><span class="o">-</span><span class="mi">10</span><span class="p">,</span> <span class="o">-</span><span class="mi">100</span><span class="p">,</span> <span class="mi">30</span><span class="p">)</span>
<span class="p">[]</span>
</pre></div>
</td></tr></table>
<p>如果迭代时需要索引和值可结合使用range()和len():</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
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9</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">a</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'Mary'</span><span class="p">,</span> <span class="s1">'had'</span><span class="p">,</span> <span class="s1">'a'</span><span class="p">,</span> <span class="s1">'little'</span><span class="p">,</span> <span class="s1">'lamb'</span><span class="p">]</span>
<span class="o">>>></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="nb">len</span><span class="p">(</span><span class="n">a</span><span class="p">)):</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">i</span><span class="p">,</span> <span class="n">a</span><span class="p">[</span><span class="n">i</span><span class="p">])</span>
<span class="o">...</span>
<span class="mi">0</span> <span class="n">Mary</span>
<span class="mi">1</span> <span class="n">had</span>
<span class="mi">2</span> <span class="n">a</span>
<span class="mi">3</span> <span class="n">little</span>
<span class="mi">4</span> <span class="n">lamb</span>
</pre></div>
</td></tr></table>
<p>不过使用enumerate()更方便，参见后面的介绍。</p>
<h3 id="breakcontinueelse">break和continue语句及循环中的else子句</h3>
<p>break语句和C中的类似，用于终止当前的for或while循环。 </p>
<p>循环可能有else 子句；它在循环迭代完整个列表(对于 for)后或执行条件为false(对于 while)时执行，但循环break时不会执行。这点和try...else而不是if...else相近。请看查找素数的程序: </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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17</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">10</span><span class="p">):</span>
<span class="o">...</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="n">n</span><span class="p">):</span>
<span class="o">...</span> <span class="k">if</span> <span class="n">n</span> <span class="o">%</span> <span class="n">x</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="s1">'equals'</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="s1">'*'</span><span class="p">,</span> <span class="n">n</span><span class="o">//</span><span class="n">x</span><span class="p">)</span>
<span class="o">...</span> <span class="k">break</span>
<span class="o">...</span> <span class="k">else</span><span class="p">:</span>
<span class="o">...</span> <span class="c1"># loop fell through without finding a factor</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="s1">'is a prime number'</span><span class="p">)</span>
<span class="o">...</span>
<span class="mi">2</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">3</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">4</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">2</span>
<span class="mi">5</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">6</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">3</span>
<span class="mi">7</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">8</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">4</span>
<span class="mi">9</span> <span class="n">equals</span> <span class="mi">3</span> <span class="o">*</span> <span class="mi">3</span>
</pre></div>
</td></tr></table>
<p>continue语句也是从C而来，它表示退出当次循环，继续执行下次迭代。通常可以用if...else替代，请看查找偶数的实例： </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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17</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">10</span><span class="p">):</span>
<span class="o">...</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="n">n</span><span class="p">):</span>
<span class="o">...</span> <span class="k">if</span> <span class="n">n</span> <span class="o">%</span> <span class="n">x</span> <span class="o">==</span> <span class="mi">0</span><span class="p">:</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="s1">'equals'</span><span class="p">,</span> <span class="n">x</span><span class="p">,</span> <span class="s1">'*'</span><span class="p">,</span> <span class="n">n</span><span class="o">//</span><span class="n">x</span><span class="p">)</span>
<span class="o">...</span> <span class="k">break</span>
<span class="o">...</span> <span class="k">else</span><span class="p">:</span>
<span class="o">...</span> <span class="c1"># loop fell through without finding a factor</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="s1">'is a prime number'</span><span class="p">)</span>
<span class="o">...</span>
<span class="mi">2</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">3</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">4</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">2</span>
<span class="mi">5</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">6</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">3</span>
<span class="mi">7</span> <span class="ow">is</span> <span class="n">a</span> <span class="n">prime</span> <span class="n">number</span>
<span class="mi">8</span> <span class="n">equals</span> <span class="mi">2</span> <span class="o">*</span> <span class="mi">4</span>
<span class="mi">9</span> <span class="n">equals</span> <span class="mi">3</span> <span class="o">*</span> <span class="mi">3</span>
</pre></div>
</td></tr></table>
<h3 id="pass">pass</h3>
<p>pass语句什么也不做。它语法上需要，但是实际什么也不做场合，也常用语以后预留以后扩展。例如: </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
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9</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">while</span> <span class="bp">True</span><span class="p">:</span>
<span class="o">...</span> <span class="k">pass</span> <span class="c1"># Busy-wait for keyboard interrupt (Ctrl+C)</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="k">class</span> <span class="nc">MyEmptyClass</span><span class="p">:</span>
<span class="o">...</span> <span class="k">pass</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="k">def</span> <span class="nf">initlog</span><span class="p">(</span><span class="o">*</span><span class="n">args</span><span class="p">):</span>
<span class="o">...</span> <span class="k">pass</span> <span class="c1"># Remember to implement this!</span>
<span class="o">...</span>
</pre></div>
</td></tr></table>
<h3 id="_2">循环技巧</h3>
<p>在字典中循环时，关键字和对应的值可以使用 items() 方法同时获取:</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2
3
4
5
6</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">knights</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'gallahad'</span><span class="p">:</span> <span class="s1">'the pure'</span><span class="p">,</span> <span class="s1">'robin'</span><span class="p">:</span> <span class="s1">'the brave'</span><span class="p">}</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">k</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="n">knights</span><span class="o">.</span><span class="n">items</span><span class="p">():</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">k</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">...</span>
<span class="n">gallahad</span> <span class="n">the</span> <span class="n">pure</span>
<span class="n">robin</span> <span class="n">the</span> <span class="n">brave</span>
</pre></div>
</td></tr></table>
<p>在序列中循环时 enumerate() 函数同时得到索引位置和对应值:</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2
3
4
5
6</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">for</span> <span class="n">i</span><span class="p">,</span> <span class="n">v</span> <span class="ow">in</span> <span class="nb">enumerate</span><span class="p">([</span><span class="s1">'tic'</span><span class="p">,</span> <span class="s1">'tac'</span><span class="p">,</span> <span class="s1">'toe'</span><span class="p">]):</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">i</span><span class="p">,</span> <span class="n">v</span><span class="p">)</span>
<span class="o">...</span>
<span class="mi">0</span> <span class="n">tic</span>
<span class="mi">1</span> <span class="n">tac</span>
<span class="mi">2</span> <span class="n">toe</span>
</pre></div>
</td></tr></table>
<p>同时循环两个或更多的序列，可以使用 zip() 打包:</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2
3
4
5
6
7
8</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">questions</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'name'</span><span class="p">,</span> <span class="s1">'quest'</span><span class="p">,</span> <span class="s1">'favorite color'</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">answers</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'lancelot'</span><span class="p">,</span> <span class="s1">'the holy grail'</span><span class="p">,</span> <span class="s1">'blue'</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">q</span><span class="p">,</span> <span class="n">a</span> <span class="ow">in</span> <span class="nb">zip</span><span class="p">(</span><span class="n">questions</span><span class="p">,</span> <span class="n">answers</span><span class="p">):</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="s1">'What is your {0}? It is {1}.'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">q</span><span class="p">,</span> <span class="n">a</span><span class="p">))</span>
<span class="o">...</span>
<span class="n">What</span> <span class="ow">is</span> <span class="n">your</span> <span class="n">name</span><span class="err">?</span> <span class="n">It</span> <span class="ow">is</span> <span class="n">lancelot</span><span class="o">.</span>
<span class="n">What</span> <span class="ow">is</span> <span class="n">your</span> <span class="n">quest</span><span class="err">?</span> <span class="n">It</span> <span class="ow">is</span> <span class="n">the</span> <span class="n">holy</span> <span class="n">grail</span><span class="o">.</span>
<span class="n">What</span> <span class="ow">is</span> <span class="n">your</span> <span class="n">favorite</span> <span class="n">color</span><span class="err">?</span> <span class="n">It</span> <span class="ow">is</span> <span class="n">blue</span><span class="o">.</span>
</pre></div>
</td></tr></table>
<p>需要逆向循环序列的话，调用 reversed() 函数即可: </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2
3
4
5
6
7
8</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">reversed</span><span class="p">(</span><span class="nb">xrange</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">2</span><span class="p">)):</span>
<span class="o">...</span> <span class="k">print</span><span class="p">(</span><span class="n">i</span><span class="p">)</span>
<span class="o">...</span>
<span class="mi">9</span>
<span class="mi">7</span>
<span class="mi">5</span>
<span class="mi">3</span>
<span class="mi">1</span>
</pre></div>
</td></tr></table>
<p>使用 sorted() 函数可排序序列，它不改动原序列，而是生成新的已排序的序列: </p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2
3
4
5
6
7
8</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">basket</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'apple'</span><span class="p">,</span> <span class="s1">'orange'</span><span class="p">,</span> <span class="s1">'apple'</span><span class="p">,</span> <span class="s1">'pear'</span><span class="p">,</span> <span class="s1">'orange'</span><span class="p">,</span> <span class="s1">'banana'</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">f</span> <span class="ow">in</span> <span class="nb">sorted</span><span class="p">(</span><span class="nb">set</span><span class="p">(</span><span class="n">basket</span><span class="p">)):</span>
<span class="o">...</span> <span class="k">print</span> <span class="n">f</span>
<span class="o">...</span>
<span class="n">apple</span>
<span class="n">banana</span>
<span class="n">orange</span>
<span class="n">pear</span>
</pre></div>
</td></tr></table>
<p>若要在循环时修改迭代的序列，建议先复制。 </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="kn">import</span> <span class="nn">math</span>
<span class="o">>>></span> <span class="n">raw_data</span> <span class="o">=</span> <span class="p">[</span><span class="mf">56.2</span><span class="p">,</span> <span class="nb">float</span><span class="p">(</span><span class="s1">'NaN'</span><span class="p">),</span> <span class="mf">51.7</span><span class="p">,</span> <span class="mf">55.3</span><span class="p">,</span> <span class="mf">52.5</span><span class="p">,</span> <span class="nb">float</span><span class="p">(</span><span class="s1">'NaN'</span><span class="p">),</span> <span class="mf">47.8</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">filtered_data</span> <span class="o">=</span> <span class="p">[]</span>
<span class="o">>>></span> <span class="k">for</span> <span class="n">value</span> <span class="ow">in</span> <span class="n">raw_data</span><span class="p">:</span>
<span class="o">...</span> <span class="k">if</span> <span class="ow">not</span> <span class="n">math</span><span class="o">.</span><span class="n">isnan</span><span class="p">(</span><span class="n">value</span><span class="p">):</span>
<span class="o">...</span> <span class="n">filtered_data</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="n">filtered_data</span>
<span class="p">[</span><span class="mf">56.2</span><span class="p">,</span> <span class="mf">51.7</span><span class="p">,</span> <span class="mf">55.3</span><span class="p">,</span> <span class="mf">52.5</span><span class="p">,</span> <span class="mf">47.8</span><span class="p">]</span>
</pre></div>
<h2 id="_3">循环</h2>
<p><img alt="image.png" src="https://upload-images.jianshu.io/upload_images/10819934-d531a59aa43d0905.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240"></p>
<p>代码：</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="c1"># -*- coding: utf-8 -*-</span>
<span class="c1"># Author: xurongzhong#126.com wechat:pythontesting qq:37391319</span>
<span class="c1"># 技术支持 钉钉群：21745728(可以加钉钉pythontesting邀请加入) </span>
<span class="c1"># qq群：144081101 591302926 567351477</span>
<span class="c1"># CreateDate: 2018-6-12 </span>
<span class="c1"># bowtie.py</span>
<span class="c1"># Draw a bowtie</span>
<span class="kn">from</span> <span class="nn">turtle</span> <span class="kn">import</span> <span class="o">*</span>
<span class="k">def</span> <span class="nf">polygon</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="n">length</span><span class="p">):</span>
<span class="sd">"""Draw n-sided polygon with given side length."""</span>
<span class="k">for</span> <span class="n">_</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="n">n</span><span class="p">):</span>
<span class="n">forward</span><span class="p">(</span><span class="n">length</span><span class="p">)</span>
<span class="n">left</span><span class="p">(</span><span class="mi">360</span><span class="o">/</span><span class="n">n</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
<span class="sd">"""Draw polygons with 3-9 sides."""</span>
<span class="k">for</span> <span class="n">n</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">10</span><span class="p">):</span>
<span class="n">polygon</span><span class="p">(</span><span class="n">n</span><span class="p">,</span> <span class="mi">80</span><span class="p">)</span>
<span class="n">exitonclick</span><span class="p">()</span>
<span class="n">main</span><span class="p">()</span>
</pre></div>
</td></tr></table>
<h2 id="while">条件循环while</h2>
<p><img alt="image.png" src="https://upload-images.jianshu.io/upload_images/10819934-d3382305df5fd8df.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240"></p>
<p>代码：</p>
<table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="c1"># -*- coding: utf-8 -*-</span>
<span class="c1"># Author: xurongzhong#126.com wechat:pythontesting qq:37391319</span>
<span class="c1"># 技术支持 钉钉群：21745728(可以加钉钉pythontesting邀请加入) </span>
<span class="c1"># qq群：144081101 591302926 567351477</span>
<span class="c1"># CreateDate: 2018-6-12 </span>
<span class="c1"># spiral.py</span>
<span class="c1"># Draw spiral shapes</span>
<span class="kn">from</span> <span class="nn">turtle</span> <span class="kn">import</span> <span class="o">*</span>
<span class="k">def</span> <span class="nf">spiral</span><span class="p">(</span><span class="n">firststep</span><span class="p">,</span> <span class="n">angle</span><span class="p">,</span> <span class="n">gap</span><span class="p">):</span>
<span class="sd">"""Move turtle on a spiral path."""</span>
<span class="n">step</span> <span class="o">=</span> <span class="n">firststep</span>
<span class="k">while</span> <span class="n">step</span> <span class="o">></span> <span class="mi">0</span><span class="p">:</span>
<span class="n">forward</span><span class="p">(</span><span class="n">step</span><span class="p">)</span>
<span class="n">left</span><span class="p">(</span><span class="n">angle</span><span class="p">)</span>
<span class="n">step</span> <span class="o">-=</span> <span class="n">gap</span>
<span class="k">def</span> <span class="nf">main</span><span class="p">():</span>
<span class="n">spiral</span><span class="p">(</span><span class="mi">100</span><span class="p">,</span> <span class="mi">71</span><span class="p">,</span> <span class="mi">2</span><span class="p">)</span>
<span class="n">exitonclick</span><span class="p">()</span>
<span class="n">main</span><span class="p">()</span>
</pre></div>
</td></tr></table>
<h2 id="_4">参考资料</h2>
<ul>
<li>python测试等IT技术支持qq群： 144081101(后期会录制视频存在该群群文件) 591302926 567351477 钉钉免费群：21745728</li>
<li>道家技术-手相手诊看相中医等钉钉群21734177 qq群：391441566 184175668 338228106 看手相、面相、舌相、抽签、体质识别。服务费50元每人次起。请联系钉钉或者微信pythontesting</li>
<li><a href="https://china-testing.github.io/python3_crash3.html">本文最新版本地址</a></li>
<li><a href="https://github.com/china-testing/python-api-tesing">本文涉及的python测试开发库</a> 谢谢点赞！</li>
<li><a href="https://github.com/china-testing/python-api-tesing/blob/master/books.md">本文相关海量书籍下载</a></li>
<li><a href="https://china-testing.github.io/testing_training.html">接口自动化性能测试线上培训大纲</a></li>
</ul>
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<h2>links</h2>
<ul>
<li><a href="https://china-testing.github.io/testing_training.html">自动化性能接口测试线上及深圳培训与项目实战 qq群：144081101 591302926</a></li>
<li><a href="http://blog.sciencenet.cn/blog-2604609-1112306.html">pandas数据分析scrapy爬虫 521070358 Py人工智能pandas-opencv 6089740</a></li>
<li><a href="http://blog.sciencenet.cn/blog-2604609-1112306.html">中医解梦看相八字算命qq群 391441566 csdn书籍下载-python爬虫 437355848</a></li>
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