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title="Permalink to [雪峰磁针石博客]python3快速入门教程2数据结构4其他数据结构">[雪峰磁针石博客]python3快速入门教程2数据结构4其他数据结构</a></h1>
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<abbr class="published" title="2018-09-02T10:40:00+08:00">
Published: 日 02 九月 2018
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By <a class="url fn" href="/author/andrew.html">andrew</a>
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<p>In <a href="/category/python.html">python</a>.</p>
</footer><!-- /.post-info --> <h2 id="_1">数据结构</h2>
<h4 id="_2">函数式编程工具</h4>
<p>对于列表来讲，有三个内置函数非常有用: filter(), map(), 以及reduce()。 </p>
<p>filter(function, sequence)返回function(item)为true的子序列。会尽量返回和sequence相同的类型）。sequence是string或者tuple时返回相同类型，其他情况返回list 。实例：返回能被3或者5整除的序列: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">def</span> <span class="nf">f</span><span class="p">(</span><span class="n">x</span><span class="p">):</span> <span class="k">return</span> <span class="n">x</span> <span class="o">%</span> <span class="mi">3</span> <span class="o">==</span> <span class="mi">0</span> <span class="ow">or</span> <span class="n">x</span> <span class="o">%</span> <span class="mi">5</span> <span class="o">==</span> <span class="mi">0</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="nb">filter</span><span class="p">(</span><span class="n">f</span><span class="p">,</span> <span class="nb">range</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">25</span><span class="p">)))</span>
<span class="p">[</span><span class="mi">3</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">9</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">15</span><span class="p">,</span> <span class="mi">18</span><span class="p">,</span> <span class="mi">20</span><span class="p">,</span> <span class="mi">21</span><span class="p">,</span> <span class="mi">24</span><span class="p">]</span>
</pre></div>
<p>map(function, sequence) 为每个元素调用 function(item)，并将返回值组成一个列表返回。例如计算立方: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">def</span> <span class="nf">cube</span><span class="p">(</span><span class="n">x</span><span class="p">):</span> <span class="k">return</span> <span class="n">x</span><span class="o">*</span><span class="n">x</span><span class="o">*</span><span class="n">x</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">cube</span><span class="p">,</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">11</span><span class="p">)))</span>
<span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">27</span><span class="p">,</span> <span class="mi">64</span><span class="p">,</span> <span class="mi">125</span><span class="p">,</span> <span class="mi">216</span><span class="p">,</span> <span class="mi">343</span><span class="p">,</span> <span class="mi">512</span><span class="p">,</span> <span class="mi">729</span><span class="p">,</span> <span class="mi">1000</span><span class="p">]</span>
</pre></div>
<p>函数需要多个参数，可以传入对应的序列。如果参数和序列数不匹配，则按最短长度来处理。如果传入的序列长度不匹配，则用None不全。例如: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">seq</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">8</span><span class="p">)</span>
<span class="o">>>></span> <span class="k">def</span> <span class="nf">add</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">return</span> <span class="n">x</span><span class="o">+</span><span class="n">y</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">seq</span><span class="p">))</span>
<span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">14</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">seq1</span> <span class="o">=</span> <span class="nb">range</span><span class="p">(</span><span class="mi">8</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">seq2</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="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="n">seq1</span><span class="p">,</span> <span class="n">seq2</span><span class="p">))</span>
<span class="p">[</span><span class="mi">0</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">6</span><span class="p">,</span> <span class="mi">8</span><span class="p">,</span> <span class="mi">10</span><span class="p">,</span> <span class="mi">12</span><span class="p">,</span> <span class="mi">14</span><span class="p">]</span>
<span class="o">>>></span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="n">seq1</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">seq2</span><span class="p">))</span>
<span class="o">---------------------------------------------------------------------------</span>
<span class="ne">TypeError</span> <span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">)</span>
<span class="o"><</span><span class="n">ipython</span><span class="o">-</span><span class="nb">input</span><span class="o">-</span><span class="mi">19</span><span class="o">-</span><span class="mi">2</span><span class="n">ddf805a1583</span><span class="o">></span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span><span class="p">()</span>
<span class="o">----></span> <span class="mi">1</span> <span class="nb">list</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="n">seq1</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="n">seq2</span><span class="p">))</span>
<span class="ne">TypeError</span><span class="p">:</span> <span class="n">add</span><span class="p">()</span> <span class="n">takes</span> <span class="mi">2</span> <span class="n">positional</span> <span class="n">arguments</span> <span class="n">but</span> <span class="mi">3</span> <span class="n">were</span> <span class="n">given</span>
</pre></div>
<p>reduce(function, sequence) 先以序列的前两个元素调用函数function，再以返回值和第三个参数调用，以此类推。比如计算 1 到 10 的整数之和: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="kn">from</span> <span class="nn">functools</span> <span class="kn">import</span> <span class="nb">reduce</span>
<span class="o">>>></span> <span class="k">def</span> <span class="nf">add</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">return</span> <span class="n">x</span><span class="o">+</span><span class="n">y</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="nb">reduce</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">11</span><span class="p">))</span>
<span class="mi">55</span>
</pre></div>
<p>如果序列中只有一个元素，就返回该元素，如果序列是空的，就报异常TypeError:</p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="nb">reduce</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="p">[])</span>
<span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span>
<span class="n">File</span> <span class="s2">"<stdin>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">1</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span>
<span class="ne">TypeError</span><span class="p">:</span> <span class="nb">reduce</span><span class="p">()</span> <span class="n">of</span> <span class="n">empty</span> <span class="n">sequence</span> <span class="k">with</span> <span class="n">no</span> <span class="n">initial</span> <span class="n">value</span>
<span class="o">>>></span> <span class="nb">reduce</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="p">[</span><span class="mi">3</span><span class="p">])</span>
<span class="mi">3</span>
</pre></div>
<p>可以传入第三个参数作为默认值。如果序列是空就返回默认值。 </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">def</span> <span class="nf">sum</span><span class="p">(</span><span class="n">seq</span><span class="p">):</span>
<span class="o">...</span> <span class="k">def</span> <span class="nf">add</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">return</span> <span class="n">x</span><span class="o">+</span><span class="n">y</span>
<span class="o">...</span> <span class="k">return</span> <span class="nb">reduce</span><span class="p">(</span><span class="n">add</span><span class="p">,</span> <span class="n">seq</span><span class="p">,</span> <span class="mi">0</span><span class="p">)</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="nb">sum</span><span class="p">(</span><span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">11</span><span class="p">))</span>
<span class="mi">55</span>
<span class="o">>>></span> <span class="nb">sum</span><span class="p">([])</span>
<span class="mi">0</span>
</pre></div>
<p>不要像示例这样定义 sum()，内置的 sum(sequence) 函数更好用。</p>
<h3 id="del">del 语句</h3>
<p>del可基于索引而不是值来删除元素。：del 语句。与 pop() 方法不同，它不返回值。del 还可以从列表中删除区间或清空整个列表。例如: </p>
<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="o">-</span><span class="mi">1</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="mf">66.25</span><span class="p">,</span> <span class="mi">333</span><span class="p">,</span> <span class="mi">333</span><span class="p">,</span> <span class="mf">1234.5</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">del</span> <span class="n">a</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">a</span>
<span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mf">66.25</span><span class="p">,</span> <span class="mi">333</span><span class="p">,</span> <span class="mi">333</span><span class="p">,</span> <span class="mf">1234.5</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">del</span> <span class="n">a</span><span class="p">[</span><span class="mi">2</span><span class="p">:</span><span class="mi">4</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">a</span>
<span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mf">66.25</span><span class="p">,</span> <span class="mf">1234.5</span><span class="p">]</span>
<span class="o">>>></span> <span class="k">del</span> <span class="n">a</span><span class="p">[:]</span>
<span class="o">>>></span> <span class="n">a</span>
<span class="p">[]</span>
</pre></div>
<p>del 也可以删除整个变量: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="k">del</span> <span class="n">a</span>
</pre></div>
<p>此后再引用a会引发错误。 </p>
<h3 id="_3">元组和序列</h3>
<p>链表和字符串有很多通用的属性，例如索引和切割操作。它们都属于序列类型(参见 Sequence Types — str, unicode, list, tuple, bytearray, buffer, xrange https://docs.python.org/2/library/stdtypes.html#typesseq)。Python在进化时也可能会加入其它的序列类型。 </p>
<p>元组由逗号分隔的值组成:</p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">t</span> <span class="o">=</span> <span class="mi">12345</span><span class="p">,</span> <span class="mi">54321</span><span class="p">,</span> <span class="s1">'hello!'</span>
<span class="o">>>></span> <span class="n">t</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span>
<span class="mi">12345</span>
<span class="o">>>></span> <span class="n">t</span>
<span class="p">(</span><span class="mi">12345</span><span class="p">,</span> <span class="mi">54321</span><span class="p">,</span> <span class="s1">'hello!'</span><span class="p">)</span>
<span class="o">>>></span> <span class="c1"># Tuples may be nested:</span>
<span class="o">...</span> <span class="n">u</span> <span class="o">=</span> <span class="n">t</span><span class="p">,</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="o">>>></span> <span class="n">u</span>
<span class="p">((</span><span class="mi">12345</span><span class="p">,</span> <span class="mi">54321</span><span class="p">,</span> <span class="s1">'hello!'</span><span class="p">),</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="o">>>></span> <span class="c1"># Tuples are immutable:</span>
<span class="o">...</span> <span class="n">t</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="mi">88888</span>
<span class="n">Traceback</span> <span class="p">(</span><span class="n">most</span> <span class="n">recent</span> <span class="n">call</span> <span class="n">last</span><span class="p">):</span>
<span class="n">File</span> <span class="s2">"<stdin>"</span><span class="p">,</span> <span class="n">line</span> <span class="mi">1</span><span class="p">,</span> <span class="ow">in</span> <span class="o"><</span><span class="n">module</span><span class="o">></span>
<span class="ne">TypeError</span><span class="p">:</span> <span class="s1">'tuple'</span> <span class="nb">object</span> <span class="n">does</span> <span class="ow">not</span> <span class="n">support</span> <span class="n">item</span> <span class="n">assignment</span>
<span class="o">>>></span> <span class="c1"># but they can contain mutable objects:</span>
<span class="o">...</span> <span class="n">v</span> <span class="o">=</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="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">v</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="p">[</span><span class="mi">3</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">1</span><span class="p">])</span>
</pre></div>
<p>元组在输出时总是有括号的，嵌套元组可以清晰展示。在输入时可以没有括号，清晰起见，建议尽量添加括号。不能给元组的的元素赋值，但可以创建包含可变对象的元组，比如列表。<br>
元组是不可变的，通常用于包含不同类型的元素，并通过解包或索引访问(collections模块中namedtuple中可以通过属性访问）。列表是可变的，元素通常是相同的类型，用于迭代。<br>
空的括号可以创建空元组；要创建一个单元素元组可以在值后面跟一个逗号单元素元组。丑陋，但是有效。例如:</p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">empty</span> <span class="o">=</span> <span class="p">()</span>
<span class="o">>>></span> <span class="n">singleton</span> <span class="o">=</span> <span class="s1">'hello'</span><span class="p">,</span> <span class="c1"># <-- note trailing comma</span>
<span class="o">>>></span> <span class="nb">len</span><span class="p">(</span><span class="n">empty</span><span class="p">)</span>
<span class="mi">0</span>
<span class="o">>>></span> <span class="nb">len</span><span class="p">(</span><span class="n">singleton</span><span class="p">)</span>
<span class="mi">1</span>
<span class="o">>>></span> <span class="n">singleton</span>
<span class="p">(</span><span class="s1">'hello'</span><span class="p">,)</span>
<span class="o">>>></span> <span class="p">(</span><span class="s1">'hello'</span><span class="p">,)</span>
<span class="p">(</span><span class="s1">'hello'</span><span class="p">,)</span>
</pre></div>
<p>语句 t = 12345, 54321, 'hello!' 是 元组打包 (tuple packing)的例子：值12345，54321 和 'hello!' 被封装进元组。其逆操作如下:</p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">x</span><span class="p">,</span> <span class="n">y</span><span class="p">,</span> <span class="n">z</span> <span class="o">=</span> <span class="n">t</span>
</pre></div>
<p>等号右边可以是任何序列，即序列解包。序列解包要求左侧的变量数目与序列的元素个数相同。</p>
<h3 id="_4">集合</h3>
<p>集合是无序不重复元素的集。基本用法有关系测试和去重。集合还支持 union(联合)，intersection(交)，difference(差)和 sysmmetric difference(对称差集)等数学运算。<br>
大括号或set()函数可以用来创建集合。注意：想要创建空集合只能使用 set() 而不是 {}。 </p>
<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="n">fruit</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="n">basket</span><span class="p">)</span> <span class="c1"># create a set without duplicates</span>
<span class="o">>>></span> <span class="n">fruit</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'orange'</span><span class="p">,</span> <span class="s1">'pear'</span><span class="p">,</span> <span class="s1">'apple'</span><span class="p">,</span> <span class="s1">'banana'</span><span class="p">])</span>
<span class="o">>>></span> <span class="s1">'orange'</span> <span class="ow">in</span> <span class="n">fruit</span> <span class="c1"># fast membership testing</span>
<span class="bp">True</span>
<span class="o">>>></span> <span class="s1">'crabgrass'</span> <span class="ow">in</span> <span class="n">fruit</span>
<span class="bp">False</span>
<span class="o">>>></span> <span class="c1"># Demonstrate set operations on unique letters from two words</span>
<span class="o">...</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="s1">'abracadabra'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">b</span> <span class="o">=</span> <span class="nb">set</span><span class="p">(</span><span class="s1">'alacazam'</span><span class="p">)</span>
<span class="o">>>></span> <span class="n">a</span> <span class="c1"># unique letters in a</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'r'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">,</span> <span class="s1">'d'</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">-</span> <span class="n">b</span> <span class="c1"># letters in a but not in b</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'r'</span><span class="p">,</span> <span class="s1">'d'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">|</span> <span class="n">b</span> <span class="c1"># letters in either a or b</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">,</span> <span class="s1">'r'</span><span class="p">,</span> <span class="s1">'d'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'m'</span><span class="p">,</span> <span class="s1">'z'</span><span class="p">,</span> <span class="s1">'l'</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">&</span> <span class="n">b</span> <span class="c1"># letters in both a and b</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'a'</span><span class="p">,</span> <span class="s1">'c'</span><span class="p">])</span>
<span class="o">>>></span> <span class="n">a</span> <span class="o">^</span> <span class="n">b</span> <span class="c1"># letters in a or b but not both</span>
<span class="nb">set</span><span class="p">([</span><span class="s1">'r'</span><span class="p">,</span> <span class="s1">'d'</span><span class="p">,</span> <span class="s1">'b'</span><span class="p">,</span> <span class="s1">'m'</span><span class="p">,</span> <span class="s1">'z'</span><span class="p">,</span> <span class="s1">'l'</span><span class="p">])</span>
</pre></div>
<p>类似列表推导式，集合也可以使用推导式: </p>
<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="n">x</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="s1">'abracadabra'</span> <span class="k">if</span> <span class="n">x</span> <span class="ow">not</span> <span class="ow">in</span> <span class="s1">'abc'</span><span class="p">}</span>
<span class="o">>>></span> <span class="n">a</span>
<span class="p">{</span><span class="s1">'r'</span><span class="p">,</span> <span class="s1">'d'</span><span class="p">}</span>
</pre></div>
<h3 id="_5">字典</h3>
<p>字典 (参见 <a href="https://docs.python.org/2/library/stdtypes.html#typesmapping">Mapping Types — dict</a> )。字典在一些语言中称为联合内存 (associative memories) 或联合数组 (associative arrays)。字典以key为索引，key可以是任意不可变类型，通常为字符串或数值。 </p>
<p>可以把字典看做无序的键：值对 (key:value对)集合。{}创建空的字典。key:value的格式，以逗号分割。 </p>
<p>字典的主要操作是依据key来读写值。用 del 可以删除key:value对。读不存在的key取值会导致错误。 </p>
<p>keys() 返回字典中所有关键字组成的无序列表。使用 in 可以判断成员关系。 </p>
<p>这里是使用字典的一个小示例: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="n">tel</span> <span class="o">=</span> <span class="p">{</span><span class="s1">'jack'</span><span class="p">:</span> <span class="mi">4098</span><span class="p">,</span> <span class="s1">'sape'</span><span class="p">:</span> <span class="mi">4139</span><span class="p">}</span>
<span class="o">>>></span> <span class="n">tel</span><span class="p">[</span><span class="s1">'guido'</span><span class="p">]</span> <span class="o">=</span> <span class="mi">4127</span>
<span class="o">>>></span> <span class="n">tel</span>
<span class="p">{</span><span class="s1">'sape'</span><span class="p">:</span> <span class="mi">4139</span><span class="p">,</span> <span class="s1">'guido'</span><span class="p">:</span> <span class="mi">4127</span><span class="p">,</span> <span class="s1">'jack'</span><span class="p">:</span> <span class="mi">4098</span><span class="p">}</span>
<span class="o">>>></span> <span class="n">tel</span><span class="p">[</span><span class="s1">'jack'</span><span class="p">]</span>
<span class="mi">4098</span>
<span class="o">>>></span> <span class="k">del</span> <span class="n">tel</span><span class="p">[</span><span class="s1">'sape'</span><span class="p">]</span>
<span class="o">>>></span> <span class="n">tel</span><span class="p">[</span><span class="s1">'irv'</span><span class="p">]</span> <span class="o">=</span> <span class="mi">4127</span>
<span class="o">>>></span> <span class="n">tel</span>
<span class="p">{</span><span class="s1">'guido'</span><span class="p">:</span> <span class="mi">4127</span><span class="p">,</span> <span class="s1">'irv'</span><span class="p">:</span> <span class="mi">4127</span><span class="p">,</span> <span class="s1">'jack'</span><span class="p">:</span> <span class="mi">4098</span><span class="p">}</span>
<span class="o">>>></span> <span class="n">tel</span><span class="o">.</span><span class="n">keys</span><span class="p">()</span>
<span class="p">[</span><span class="s1">'guido'</span><span class="p">,</span> <span class="s1">'irv'</span><span class="p">,</span> <span class="s1">'jack'</span><span class="p">]</span>
<span class="o">>>></span> <span class="s1">'guido'</span> <span class="ow">in</span> <span class="n">tel</span>
<span class="bp">True</span>
</pre></div>
<p>dict() 构造函数可以直接从 key-value 序列中创建字典: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="nb">dict</span><span class="p">([(</span><span class="s1">'sape'</span><span class="p">,</span> <span class="mi">4139</span><span class="p">),</span> <span class="p">(</span><span class="s1">'guido'</span><span class="p">,</span> <span class="mi">4127</span><span class="p">),</span> <span class="p">(</span><span class="s1">'jack'</span><span class="p">,</span> <span class="mi">4098</span><span class="p">)])</span>
<span class="p">{</span><span class="s1">'sape'</span><span class="p">:</span> <span class="mi">4139</span><span class="p">,</span> <span class="s1">'jack'</span><span class="p">:</span> <span class="mi">4098</span><span class="p">,</span> <span class="s1">'guido'</span><span class="p">:</span> <span class="mi">4127</span><span class="p">}</span>
</pre></div>
<p>字典推导式可以从任意的键值表达式中创建字典: </p>
<div class="highlight"><pre><span></span><span class="o">>>></span> <span class="p">{</span><span class="n">x</span><span class="p">:</span> <span class="n">x</span><span class="o">**</span><span class="mi">2</span> <span class="k">for</span> <span class="n">x</span> <span class="ow">in</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">6</span><span class="p">)}</span>
<span class="p">{</span><span class="mi">2</span><span class="p">:</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">4</span><span class="p">:</span> <span class="mi">16</span><span class="p">,</span> <span class="mi">6</span><span class="p">:</span> <span class="mi">36</span><span class="p">}</span>
</pre></div>
<p>如果关键字都是简单的字符串，可通过关键字参数指定 key-value 对: </p>
<div class="highlight"><pre><span></span>>>> dict(sape=4139, guido=4127, jack=4098)
{'sape': 4139, 'jack': 4098, 'guido': 4127}
</pre></div>
<h3 id="_6">序列和其它类型比较</h3>
<p>序列对象可以与相同类型的其它对象比较。比较基于字典序：首先比较前两个元素，如果不同，就决定了比较的结果；如果相同，就比较后两个元素，依此类推，直到有序列结束。如果两个元素是同样类型的序列，就递归比较。如果两个序列的所有子项都相等则序列相等。如果一个序列是另一个序列的初始子序列，较短的序列就小于另一个。字符串的字典序基于ASCII。</p>
<div class="highlight"><pre><span></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="o"><</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">4</span><span class="p">)</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="o"><</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">4</span><span class="p">]</span>
<span class="s1">'ABC'</span> <span class="o"><</span> <span class="s1">'C'</span> <span class="o"><</span> <span class="s1">'Pascal'</span> <span class="o"><</span> <span class="s1">'Python'</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="o"><</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">4</span><span class="p">)</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="o"><</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="o">-</span><span class="mi">1</span><span class="p">)</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="o">==</span> <span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="mf">2.0</span><span class="p">,</span> <span class="mf">3.0</span><span class="p">)</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="p">(</span><span class="s1">'aa'</span><span class="p">,</span> <span class="s1">'ab'</span><span class="p">))</span> <span class="o"><</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="p">(</span><span class="s1">'abc'</span><span class="p">,</span> <span class="s1">'a'</span><span class="p">),</span> <span class="mi">4</span><span class="p">)</span>
</pre></div>
<p>注意可以比较不同类型的对象也是合法的。比较结果是确定的但是比较随意： 基于类型名(Python未来版本中可能发生变化)排序。因此，列表始终小于字符串，字符串总是小于元组，等等。 不同数值类型按照它们的值比较，所以 0 等于 0.0，等等。 </p>
<h2 id="_7">计算不同版本人脸识别框的重合面积</h2>
<p>现有某图片，版本1识别的坐标为：(60, 188, 260, 387)，版本2识别的坐标为(106, 291, 340, 530)))。格式为left, top, right, buttom。
请计算：公共的像素总数，版本1的像素总数，版本2的像素总数，版本1的重合面积比例，版本2的重合面积比例.</p>
<p>参考代码：</p>
<div class="highlight"><pre><span></span><span class="ch">#!/usr/bin/python3</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: 2018-6-07</span>
<span class="k">def</span> <span class="nf">get_area</span><span class="p">(</span><span class="n">pos</span><span class="p">):</span>
<span class="n">left</span><span class="p">,</span> <span class="n">top</span><span class="p">,</span> <span class="n">right</span><span class="p">,</span> <span class="n">buttom</span> <span class="o">=</span> <span class="n">pos</span>
<span class="n">left</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">left</span><span class="p">)</span>
<span class="n">top</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">top</span><span class="p">)</span>
<span class="n">width</span> <span class="o">=</span> <span class="n">right</span> <span class="o">-</span> <span class="n">left</span>
<span class="n">height</span> <span class="o">=</span> <span class="n">buttom</span> <span class="o">-</span> <span class="n">top</span>
<span class="k">return</span> <span class="p">(</span><span class="n">width</span><span class="o">*</span><span class="n">height</span><span class="p">,</span> <span class="n">left</span><span class="p">,</span> <span class="n">top</span><span class="p">,</span> <span class="n">right</span><span class="p">,</span> <span class="n">buttom</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">overlap</span><span class="p">(</span><span class="n">pos1</span><span class="p">,</span> <span class="n">pos2</span><span class="p">):</span>
<span class="n">area1</span><span class="p">,</span> <span class="n">left1</span><span class="p">,</span> <span class="n">top1</span><span class="p">,</span> <span class="n">right1</span><span class="p">,</span> <span class="n">buttom1</span> <span class="o">=</span> <span class="n">get_area</span><span class="p">(</span><span class="n">pos1</span><span class="p">)</span>
<span class="n">area2</span><span class="p">,</span> <span class="n">left2</span><span class="p">,</span> <span class="n">top2</span><span class="p">,</span> <span class="n">right2</span><span class="p">,</span> <span class="n">buttom2</span> <span class="o">=</span> <span class="n">get_area</span><span class="p">(</span><span class="n">pos2</span><span class="p">)</span>
<span class="n">left</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="n">left1</span><span class="p">,</span> <span class="n">left2</span><span class="p">)</span>
<span class="n">top</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="n">top1</span><span class="p">,</span> <span class="n">top2</span><span class="p">)</span>
<span class="n">left</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">left</span><span class="p">)</span>
<span class="n">top</span> <span class="o">=</span> <span class="nb">max</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="n">top</span><span class="p">)</span>
<span class="n">right</span> <span class="o">=</span> <span class="nb">min</span><span class="p">(</span><span class="n">right1</span><span class="p">,</span> <span class="n">right2</span><span class="p">)</span>
<span class="n">buttom</span> <span class="o">=</span> <span class="nb">min</span><span class="p">(</span><span class="n">buttom1</span><span class="p">,</span> <span class="n">buttom2</span><span class="p">)</span>
<span class="k">if</span> <span class="n">right</span> <span class="o"><=</span> <span class="n">left</span> <span class="ow">or</span> <span class="n">buttom</span> <span class="o"><=</span> <span class="n">top</span><span class="p">:</span>
<span class="n">area</span> <span class="o">=</span> <span class="mi">0</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">area</span> <span class="o">=</span> <span class="p">(</span><span class="n">right</span> <span class="o">-</span> <span class="n">left</span><span class="p">)</span><span class="o">*</span><span class="p">(</span><span class="n">buttom</span> <span class="o">-</span> <span class="n">top</span><span class="p">)</span>
<span class="k">return</span> <span class="p">(</span><span class="n">area</span><span class="p">,</span> <span class="n">area1</span><span class="p">,</span> <span class="n">area2</span><span class="p">,</span> <span class="nb">float</span><span class="p">(</span><span class="n">area</span><span class="p">)</span><span class="o">/</span><span class="n">area1</span><span class="p">,</span> <span class="nb">float</span><span class="p">(</span><span class="n">area</span><span class="p">)</span><span class="o">/</span><span class="n">area2</span><span class="p">)</span>
<span class="k">print</span><span class="p">(</span><span class="n">overlap</span><span class="p">((</span><span class="mi">60</span><span class="p">,</span> <span class="mi">188</span><span class="p">,</span> <span class="mi">260</span><span class="p">,</span> <span class="mi">387</span><span class="p">),</span> <span class="p">(</span><span class="mi">106</span><span class="p">,</span> <span class="mi">291</span><span class="p">,</span> <span class="mi">340</span><span class="p">,</span> <span class="mi">530</span><span class="p">)))</span>
</pre></div>
<p><a href="https://github.com/china-testing/python-api-tesing/tree/master/weeks/2018_06_07">详细代码地址</a></p>
<p>执行</p>
<div class="highlight"><pre><span></span><span class="err">$</span> <span class="n">python3</span> <span class="n">overlap</span><span class="o">.</span><span class="n">py</span>
<span class="p">(</span><span class="mi">14784</span><span class="p">,</span> <span class="mi">39800</span><span class="p">,</span> <span class="mi">55926</span><span class="p">,</span> <span class="mf">0.3714572864321608</span><span class="p">,</span> <span class="mf">0.2643493187426242</span><span class="p">)</span>
</pre></div>
<h2 id="_8">参考资料</h2>
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<li><a href="https://china-testing.github.io/python3_crash8.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>
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<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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