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diff --git a/LectureNotesOnPython.html b/LectureNotesOnPython.html index f56596b..600059c 100644 --- a/LectureNotesOnPython.html +++ b/LectureNotesOnPython.html @@ -376,58 +376,59 @@ ul.auto-toc { <div class="contents topic" id="id1"> <p class="topic-title first">内容目录</p> <ul class="simple"> -<li><a class="reference internal" href="#id2" id="id24">前言</a></li> -<li><a class="reference internal" href="#python" id="id25">Python的发音纠正</a></li> -<li><a class="reference internal" href="#id3" id="id26">Python源流</a></li> -<li><a class="reference internal" href="#id4" id="id27">Python的关键词</a></li> -<li><a class="reference internal" href="#id5" id="id28">值的类型</a></li> -<li><a class="reference internal" href="#variable" id="id29">变量（Variable）</a></li> -<li><a class="reference internal" href="#mutable" id="id30">可变（mutable）类型与不可变类型</a></li> -<li><a class="reference internal" href="#id6" id="id31">数与格式化显示</a></li> -<li><a class="reference internal" href="#strings" id="id32">字符串（Strings）</a></li> -<li><a class="reference internal" href="#concatenation" id="id33">字符串相加（concatenation）</a></li> -<li><a class="reference internal" href="#slice" id="id34">子串（slice）</a></li> -<li><a class="reference internal" href="#id7" id="id35">搜索字符串</a></li> -<li><a class="reference internal" href="#string" id="id36">String类（对象）方法</a></li> -<li><a class="reference internal" href="#in" id="id37">in操作符</a></li> -<li><a class="reference internal" href="#id8" id="id38">字符串比较</a></li> -<li><a class="reference internal" href="#id9" id="id39">列表</a></li> -<li><a class="reference internal" href="#id10" id="id40">列表作为参数</a></li> -<li><a class="reference internal" href="#append" id="id41">注意区别 <tt class="docutils literal">append</tt> 与 <tt class="docutils literal">+</tt> 操作符</a><ul> -<li><a class="reference internal" href="#tdd-test-driven-development" id="id42">TDD - Test-driven Development</a></li> -<li><a class="reference internal" href="#id11" id="id43">计算复杂度</a></li> +<li><a class="reference internal" href="#id2" id="id25">前言</a></li> +<li><a class="reference internal" href="#python" id="id26">Python的发音纠正</a></li> +<li><a class="reference internal" href="#id3" id="id27">Python源流</a></li> +<li><a class="reference internal" href="#id4" id="id28">Python的关键词</a></li> +<li><a class="reference internal" href="#id5" id="id29">值的类型</a></li> +<li><a class="reference internal" href="#variable" id="id30">变量（Variable）</a></li> +<li><a class="reference internal" href="#mutable" id="id31">可变（mutable）类型与不可变类型</a></li> +<li><a class="reference internal" href="#id6" id="id32">数与格式化显示</a></li> +<li><a class="reference internal" href="#strings" id="id33">字符串（Strings）</a></li> +<li><a class="reference internal" href="#concatenation" id="id34">字符串相加（concatenation）</a></li> +<li><a class="reference internal" href="#slice" id="id35">子串（slice）</a></li> +<li><a class="reference internal" href="#id7" id="id36">搜索字符串</a></li> +<li><a class="reference internal" href="#string" id="id37">String类（对象）方法</a></li> +<li><a class="reference internal" href="#in" id="id38">in操作符</a></li> +<li><a class="reference internal" href="#id8" id="id39">字符串比较</a></li> +<li><a class="reference internal" href="#id9" id="id40">列表</a></li> +<li><a class="reference internal" href="#id10" id="id41">列表作为参数</a></li> +<li><a class="reference internal" href="#append" id="id42">注意区别 <tt class="docutils literal">append</tt> 与 <tt class="docutils literal">+</tt> 操作符</a><ul> +<li><a class="reference internal" href="#tdd-test-driven-development" id="id43">TDD - Test-driven Development</a></li> +<li><a class="reference internal" href="#id11" id="id44">计算复杂度</a></li> </ul> </li> -<li><a class="reference internal" href="#dictionary" id="id44">字典（Dictionary）</a><ul> -<li><a class="reference internal" href="#incremental-development" id="id45">递增开发（Incremental Development）</a></li> -<li><a class="reference internal" href="#keyvalue" id="id46">key与value互换</a></li> -<li><a class="reference internal" href="#id12" id="id47">字典里面可以有字典</a></li> +<li><a class="reference internal" href="#dictionary" id="id45">字典（Dictionary）</a><ul> +<li><a class="reference internal" href="#incremental-development" id="id46">递增开发（Incremental Development）</a></li> +<li><a class="reference internal" href="#keyvalue" id="id47">key与value互换</a></li> +<li><a class="reference internal" href="#id12" id="id48">字典里面可以有字典</a></li> </ul> </li> -<li><a class="reference internal" href="#id13" id="id48">函数</a><ul> -<li><a class="reference internal" href="#id14" id="id49">局部变量</a></li> -<li><a class="reference internal" href="#id15" id="id50">全局变量</a></li> -<li><a class="reference internal" href="#id16" id="id51">调用函数与传递参数</a></li> -<li><a class="reference internal" href="#flow-of-execution" id="id52">函数执行顺序 （flow of execution）</a></li> +<li><a class="reference internal" href="#id13" id="id49">函数</a><ul> +<li><a class="reference internal" href="#id14" id="id50">局部变量</a></li> +<li><a class="reference internal" href="#id15" id="id51">全局变量</a></li> +<li><a class="reference internal" href="#id16" id="id52">调用函数与传递参数</a></li> +<li><a class="reference internal" href="#flow-of-execution" id="id53">函数执行顺序 （flow of execution）</a></li> </ul> </li> -<li><a class="reference internal" href="#id17" id="id53">排序</a><ul> -<li><a class="reference internal" href="#id18" id="id54">排序一组数或一组字符串</a></li> -<li><a class="reference internal" href="#id19" id="id55">自定义排序算法</a><ul> -<li><a class="reference internal" href="#id20" id="id56">选择排序</a></li> -<li><a class="reference internal" href="#merge-sort" id="id57">合并排序 （Merge sort）</a></li> +<li><a class="reference internal" href="#id17" id="id54">文件</a></li> +<li><a class="reference internal" href="#id18" id="id55">排序</a><ul> +<li><a class="reference internal" href="#id19" id="id56">排序一组数或一组字符串</a></li> +<li><a class="reference internal" href="#id20" id="id57">自定义排序算法</a><ul> +<li><a class="reference internal" href="#id21" id="id58">选择排序</a></li> +<li><a class="reference internal" href="#merge-sort" id="id59">合并排序 （Merge sort）</a></li> </ul> </li> -<li><a class="reference internal" href="#id21" id="id58">比较排序速度</a></li> -<li><a class="reference internal" href="#id22" id="id59">排序元组列表</a></li> -<li><a class="reference internal" href="#lambda" id="id60">巧用 lambda 函数进行灵活排序</a></li> +<li><a class="reference internal" href="#id22" id="id60">比较排序速度</a></li> +<li><a class="reference internal" href="#id23" id="id61">排序元组列表</a></li> +<li><a class="reference internal" href="#lambda" id="id62">巧用 lambda 函数进行灵活排序</a></li> </ul> </li> -<li><a class="reference internal" href="#id23" id="id61">参考</a></li> +<li><a class="reference internal" href="#id24" id="id63">参考</a></li> </ul> </div> <div class="section" id="id2"> -<h1><a class="toc-backref" href="#id24">前言</a></h1> +<h1><a class="toc-backref" href="#id25">前言</a></h1> <p>非学究写书，无空洞行文。</p> <p>Python语法简洁，库函数全面强大，编程速度快，运行速度也不慢。</p> <p>大学里， 往往是专家教初学者。 专家也是从初学者过来的，只不过专家经常忘 @@ -449,12 +450,12 @@ ul.auto-toc { 初学者说“我明白了”。</p> </div> <div class="section" id="python"> -<h1><a class="toc-backref" href="#id25">Python的发音纠正</a></h1> +<h1><a class="toc-backref" href="#id26">Python的发音纠正</a></h1> <p>国人普遍把th发作s。 Not quite correct。</p> <p>ˈpī-ˌthän , -thən <a class="reference external" href="https://cn.bing.com/search?q=define%20python&tf=U2VydmljZT1EaWN0aW9uYXJ5QW5zd2VyVjIgU2NlbmFyaW89RGVmaW5pdGlvblNjZW5hcmlvIFBvc2l0aW9uPU5PUCBSYW5raW5nRGF0YT1UcnVlIEZvcmNlUGxhY2U9RmFsc2UgUGFpcnM9RGljdGlvbmFyeVdvcmQ6cHl0aG9uO3NjbjpEZWZpbml0aW9uU2NlbmFyaW87cDpRQVM7IHw%3d&hs=hyRBF0mYq9hrfQUq66DIZnFVta1ZGRfBiBks25oUguk%3d">pronounciation</a></p> </div> <div class="section" id="id3"> -<h1><a class="toc-backref" href="#id26">Python源流</a></h1> +<h1><a class="toc-backref" href="#id27">Python源流</a></h1> <p>Python之父Guido van Rossum，荷兰人，1956年生，1982年阿姆斯特丹大学获得 数学与计算机科学硕士学位。有过ABC语言的工作经验。1989年设计了Python语 言。</p> @@ -504,7 +505,7 @@ ul.auto-toc { </blockquote> </div> <div class="section" id="id4"> -<h1><a class="toc-backref" href="#id27">Python的关键词</a></h1> +<h1><a class="toc-backref" href="#id28">Python的关键词</a></h1> <div class="line-block"> <div class="line">def pass</div> <div class="line">from import</div> @@ -526,7 +527,7 @@ ul.auto-toc { <p>关键词被语言留用（reserved），无法作变量名。</p> </div> <div class="section" id="id5"> -<h1><a class="toc-backref" href="#id28">值的类型</a></h1> +<h1><a class="toc-backref" href="#id29">值的类型</a></h1> <p>所有的值都是对象。a = 5, help(a) a.bit_length()</p> <p>数字。1， 1.，1.1， .1, 1e1, 1e-1, 1E1, 1E-1</p> <dl class="docutils"> @@ -546,7 +547,7 @@ A list of objects</dd> <p>元组（tuple），字典（dict）。</p> </div> <div class="section" id="variable"> -<h1><a class="toc-backref" href="#id29">变量（Variable）</a></h1> +<h1><a class="toc-backref" href="#id30">变量（Variable）</a></h1> <p>是一个名字（name），是指向一个值（value）的名字。</p> <p>值存放在内存（memory）中的某个地址。</p> <p>尽量选有意义的简短的名字。比如，代表个数用n，代表索引用i，j，k。</p> @@ -635,7 +636,7 @@ A list of objects</dd> </ul> </div> <div class="section" id="mutable"> -<h1><a class="toc-backref" href="#id30">可变（mutable）类型与不可变类型</a></h1> +<h1><a class="toc-backref" href="#id31">可变（mutable）类型与不可变类型</a></h1> <p>字符串是不可变的（immutable）类型，不能在原内存地址改变。</p> <p>a = 'hello' 不可以原地修改a[0] = 'H'。需要修改a的值时，需要对a进行重新赋值a = 'Hello'。</p> <p>列表是可变（mutable）类型，能在原内存地址改变。</p> @@ -660,7 +661,7 @@ A list of objects</dd> </blockquote> </div> <div class="section" id="id6"> -<h1><a class="toc-backref" href="#id31">数与格式化显示</a></h1> +<h1><a class="toc-backref" href="#id32">数与格式化显示</a></h1> <blockquote> <div class="line-block"> <div class="line">x = 3.1415926</div> @@ -708,7 +709,7 @@ A list of objects</dd> </blockquote> </div> <div class="section" id="strings"> -<h1><a class="toc-backref" href="#id32">字符串（Strings）</a></h1> +<h1><a class="toc-backref" href="#id33">字符串（Strings）</a></h1> <p>由字符组成。</p> <div class="line-block"> <div class="line">fruit = 'banana!'</div> @@ -764,7 +765,7 @@ A list of objects</dd> <p>以上 <tt class="docutils literal"># [start,stop,step]</tt> 代表注释（comment），注释以 <tt class="docutils literal">#</tt> 号开头。</p> </div> <div class="section" id="concatenation"> -<h1><a class="toc-backref" href="#id33">字符串相加（concatenation）</a></h1> +<h1><a class="toc-backref" href="#id34">字符串相加（concatenation）</a></h1> <p>输出Jack, Kack, Lack, Mack, Nack, Ouack, Pack, and Quack</p> <div class="line-block"> <div class="line">prefixes = 'JKLMNOPQ'</div> @@ -783,7 +784,7 @@ A list of objects</dd> </div> </div> <div class="section" id="slice"> -<h1><a class="toc-backref" href="#id34">子串（slice）</a></h1> +<h1><a class="toc-backref" href="#id35">子串（slice）</a></h1> <p>s[n:m]，其中n或m可省略。 包括第n个字符，不包括第m个字符。（索引自0开始）</p> <div class="line-block"> @@ -807,7 +808,7 @@ A list of objects</dd> </div> </div> <div class="section" id="id7"> -<h1><a class="toc-backref" href="#id35">搜索字符串</a></h1> +<h1><a class="toc-backref" href="#id36">搜索字符串</a></h1> <div class="line-block"> <div class="line">def find(word, c):</div> <div class="line-block"> @@ -833,7 +834,7 @@ A list of objects</dd> <p>练习：用上面三参数的find来做。</p> </div> <div class="section" id="string"> -<h1><a class="toc-backref" href="#id36">String类（对象）方法</a></h1> +<h1><a class="toc-backref" href="#id37">String类（对象）方法</a></h1> <div class="line-block"> <div class="line">upper()</div> <div class="line">lower()</div> @@ -846,14 +847,14 @@ A list of objects</dd> </div> </div> <div class="section" id="in"> -<h1><a class="toc-backref" href="#id37">in操作符</a></h1> +<h1><a class="toc-backref" href="#id38">in操作符</a></h1> <p>'a' in 'banana' 'seed' in 'banana'</p> <p>练习：写出下面的函数，使得 in_both('apples', 'oranges')返回'aes'。</p> </div> <div class="section" id="id8"> -<h1><a class="toc-backref" href="#id38">字符串比较</a></h1> +<h1><a class="toc-backref" href="#id39">字符串比较</a></h1> <p>字典序（alphabetical order）。大写字母排在小写字母前。</p> <p>字符串之间可以有以下对比操作:</p> <div class="line-block"> @@ -869,7 +870,7 @@ in_both('apples', 'oranges')返回'aes'。</p> <p>即兴定义函数，制造一个长度不小于4的密码。</p> </div> <div class="section" id="id9"> -<h1><a class="toc-backref" href="#id39">列表</a></h1> +<h1><a class="toc-backref" href="#id40">列表</a></h1> <p>语言的内置（built-in）类型。注意与String类比，index也是从0开始， in操作符， 求长度，获得字串，遍历操作类似。</p> <blockquote> <div class="line-block"> @@ -987,7 +988,7 @@ a与b是指向[1,2,3]的两个references。 error-prone（易错）</p> </div> <div class="section" id="id10"> -<h1><a class="toc-backref" href="#id40">列表作为参数</a></h1> +<h1><a class="toc-backref" href="#id41">列表作为参数</a></h1> <blockquote> <div class="line-block"> <div class="line">def delete_head(t):</div> @@ -1003,7 +1004,7 @@ error-prone（易错）</p> </blockquote> </div> <div class="section" id="append"> -<h1><a class="toc-backref" href="#id41">注意区别 <tt class="docutils literal">append</tt> 与 <tt class="docutils literal">+</tt> 操作符</a></h1> +<h1><a class="toc-backref" href="#id42">注意区别 <tt class="docutils literal">append</tt> 与 <tt class="docutils literal">+</tt> 操作符</a></h1> <blockquote> <div class="line-block"> <div class="line">t1 = [1, 2]</div> @@ -1030,7 +1031,7 @@ error-prone（易错）</p> </dl> </blockquote> <div class="section" id="tdd-test-driven-development"> -<h2><a class="toc-backref" href="#id42">TDD - Test-driven Development</a></h2> +<h2><a class="toc-backref" href="#id43">TDD - Test-driven Development</a></h2> <p>测试驱动开发。 My favourite。 刺激有挑战性。 帮助厘清需求。 帮助编写代码。</p> <p>推荐使用pytest。如何安装？ 使用命令 <tt class="docutils literal">pip install pytest</tt>。</p> <p>在 <tt class="docutils literal">test_cases.py</tt> 写如下测试用例。然后在命令行运行： <tt class="docutils literal">python <span class="pre">-m</span> pytest test_cases.py</tt> 。</p> @@ -1070,13 +1071,13 @@ error-prone（易错）</p> </pre> </div> <div class="section" id="id11"> -<h2><a class="toc-backref" href="#id43">计算复杂度</a></h2> +<h2><a class="toc-backref" href="#id44">计算复杂度</a></h2> <p>用Big O表述复杂度。O(n)， O(n^2), O(n^3)。</p> <p>密码实验回顾。</p> </div> </div> <div class="section" id="dictionary"> -<h1><a class="toc-backref" href="#id44">字典（Dictionary）</a></h1> +<h1><a class="toc-backref" href="#id45">字典（Dictionary）</a></h1> <p>Mutable数据类型。</p> <p>实际开发中超级有用。</p> <blockquote> @@ -1100,7 +1101,7 @@ error-prone（易错）</p> <p>key-value pair (item)</p> <p>item的顺序不可预测，不是按照创建时的顺序。</p> <div class="section" id="incremental-development"> -<h2><a class="toc-backref" href="#id45">递增开发（Incremental Development）</a></h2> +<h2><a class="toc-backref" href="#id46">递增开发（Incremental Development）</a></h2> <p>每次完成一小点。从易到难。</p> <p>练习：给定一个字符串，数出每个字母出现的频率。</p> <pre class="code python literal-block"> @@ -1208,7 +1209,7 @@ error-prone（易错）</p> <p>练习： 改写函数 <tt class="docutils literal">word_frequency</tt> ， 使它能接受第三个参数， <tt class="docutils literal">black_lst</tt>。 <tt class="docutils literal">black_lst</tt> 是包含要排除考虑的单词的列表。 例如， <tt class="docutils literal">black_lst</tt> 可以是 <tt class="docutils literal">['the', 'and', 'of', 'to']</tt> 。</p> </div> <div class="section" id="keyvalue"> -<h2><a class="toc-backref" href="#id46">key与value互换</a></h2> +<h2><a class="toc-backref" href="#id47">key与value互换</a></h2> <p>注意到在原来的字典中一个value可能对应多个key的值。比如 <tt class="docutils literal">d = <span class="pre">{'a':1,</span> <span class="pre">'b':2,</span> <span class="pre">'c':2}</span></tt> 中，2就对应两个key，'b'与'c'。</p> <pre class="code python literal-block"> <span class="keyword">def</span> <span class="name function">inverse_dictionary</span><span class="punctuation">(</span><span class="name">d</span><span class="punctuation">):</span> @@ -1245,14 +1246,14 @@ error-prone（易错）</p> </pre> </div> <div class="section" id="id12"> -<h2><a class="toc-backref" href="#id47">字典里面可以有字典</a></h2> +<h2><a class="toc-backref" href="#id48">字典里面可以有字典</a></h2> <pre class="code python literal-block"> <span class="name">d</span> <span class="operator">=</span> <span class="punctuation">{</span> <span class="literal string single">'john'</span><span class="punctuation">:{</span><span class="literal string single">'dob'</span><span class="punctuation">:</span><span class="literal string single">'1990-10-23'</span><span class="punctuation">,</span> <span class="literal string single">'height'</span><span class="punctuation">:</span><span class="literal string single">'6 feet 5 inches'</span><span class="punctuation">}</span> <span class="punctuation">}</span> </pre> </div> </div> <div class="section" id="id13"> -<h1><a class="toc-backref" href="#id48">函数</a></h1> +<h1><a class="toc-backref" href="#id49">函数</a></h1> <p>当我们开始不断复制黏贴代码时，就要考虑把这部分代码做成函数了。</p> <p>函数 <tt class="docutils literal">unique_words</tt> 与 <tt class="docutils literal">unique_words2</tt> 哪个运行速度快？</p> <pre class="code python literal-block"> @@ -1271,11 +1272,11 @@ error-prone（易错）</p> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">unique_words2</span><span class="punctuation">([</span><span class="literal string single">'hello'</span><span class="punctuation">,</span> <span class="literal string single">'world'</span><span class="punctuation">,</span> <span class="literal string single">'am'</span><span class="punctuation">,</span> <span class="literal string single">'he'</span><span class="punctuation">]</span> <span class="operator">*</span> <span class="name">N</span><span class="punctuation">))</span> </pre> <div class="section" id="id14"> -<h2><a class="toc-backref" href="#id49">局部变量</a></h2> +<h2><a class="toc-backref" href="#id50">局部变量</a></h2> <p>在函数之内。函数执行结束，局部变量消失。</p> </div> <div class="section" id="id15"> -<h2><a class="toc-backref" href="#id50">全局变量</a></h2> +<h2><a class="toc-backref" href="#id51">全局变量</a></h2> <p>全局变量位于函数之外，模块之内。全局变量对所有模块内的函数可见（可读）。如果在函数内要对全局变量重新赋值，那么要先用 <tt class="docutils literal">global</tt> 声明之 （declare）。</p> <pre class="code python literal-block"> <span class="name">verbose</span> <span class="operator">=</span> <span class="name builtin pseudo">True</span> @@ -1325,7 +1326,7 @@ error-prone（易错）</p> <p>练习： 定义一个函数 <tt class="docutils literal">empty_dict</tt> 清空字典 <tt class="docutils literal">record</tt>。 要求: 不能用 <tt class="docutils literal">return</tt> 语句。 提示： 可以用 <tt class="docutils literal">pop</tt> 方法， 或者直接给 <tt class="docutils literal">record</tt> 赋值 <tt class="docutils literal">{}</tt> 。</p> </div> <div class="section" id="id16"> -<h2><a class="toc-backref" href="#id51">调用函数与传递参数</a></h2> +<h2><a class="toc-backref" href="#id52">调用函数与传递参数</a></h2> <p>在使用函数前要先确定函数已经被定义。</p> <p>区别 <tt class="docutils literal">argument</tt> 与 <tt class="docutils literal">parameter</tt> 。传过去的是 <tt class="docutils literal">argument</tt> ， 函数头的参数列表是 <tt class="docutils literal">parameter</tt> 。 <tt class="docutils literal">argument</tt> 的值赋给 <tt class="docutils literal">parameter</tt> ， <tt class="docutils literal">parameter</tt> 是函数的局部变量。</p> <p><tt class="docutils literal">argument</tt> 与 <tt class="docutils literal">parameter</tt> 的名字可以相同也可以不同。</p> @@ -1346,17 +1347,105 @@ error-prone（易错）</p> <p>以上 t 一个是全局变量一个是局部变量。</p> </div> <div class="section" id="flow-of-execution"> -<h2><a class="toc-backref" href="#id52">函数执行顺序 （flow of execution）</a></h2> +<h2><a class="toc-backref" href="#id53">函数执行顺序 （flow of execution）</a></h2> <p>函数的定义不执行，被调用时才执行。</p> <p>顺序执行。 当遇到函数调用时，跳转到函数，执行函数，函数返回后继续执行跳转地后一条语句。</p> </div> </div> <div class="section" id="id17"> -<h1><a class="toc-backref" href="#id53">排序</a></h1> +<h1><a class="toc-backref" href="#id54">文件</a></h1> +<p>信息多存储在文件中。所以文件的读写是最最常见的操作。 本节主要考虑纯文本文件。 以下后缀结尾的文件一般都是纯文本文件: txt, csv, html, rst, md。</p> +<dl class="docutils"> +<dt>实验： 读取纽约新生儿的名字统计文件 <a class="reference external" href="https://data.cityofnewyork.us/api/views/25th-nujf/rows.csv?accessType=DOWNLOAD">PopularBabyNames</a> 。</dt> +<dd>写命令行程序 lookupname.py 。给定性别与种族，输出最流行的头几个名字。 +命令行例子： <tt class="docutils literal">python lookupname.py girl white top5</tt> 。 这个命令输出最流行的5个白人女孩的名字。 +第一个参数可以是 <tt class="docutils literal">girl/boy</tt> ， 第二个参数可以是 <tt class="docutils literal">asian/white/black/hispanic</tt> 。第三个参数以 <tt class="docutils literal">top</tt> 开始，默认是 1。</dd> +</dl> +<pre class="code python literal-block"> +<span class="comment single"># Copyright (C) 2019 Hui Lan</span> +<span class="comment single"># lanhui AT zjnu.edu.cn</span> +<span class="comment single"># Purpose: 1. Introduce command line argument parsing. 2. Introduce nested dictionaries.</span> +<span class="comment single"># Usage:</span> +<span class="comment single"># python lookupname.py asian boy top10</span> +<span class="comment single"># python lookupname.py white girl top5</span> +<span class="comment single"># python lookupname.py girl white top</span> + + +<span class="keyword">def</span> <span class="name function">map</span><span class="punctuation">(</span><span class="name">x</span><span class="punctuation">):</span> + <span class="name">d</span> <span class="operator">=</span> <span class="punctuation">{</span><span class="literal string single">'FEMALE'</span><span class="punctuation">:</span><span class="literal string single">'girl'</span><span class="punctuation">,</span> <span class="literal string single">'MALE'</span><span class="punctuation">:</span><span class="literal string single">'boy'</span><span class="punctuation">,</span> <span class="literal string single">'ASIAN AND PACIFIC ISLANDER'</span><span class="punctuation">:</span><span class="literal string single">'asian'</span><span class="punctuation">,</span> <span class="literal string single">'ASIAN AND PACI'</span><span class="punctuation">:</span><span class="literal string single">'asian'</span><span class="punctuation">,</span> + <span class="literal string single">'BLACK NON HISPANIC'</span><span class="punctuation">:</span><span class="literal string single">'black'</span><span class="punctuation">,</span> <span class="literal string single">'BLACK NON HISP'</span><span class="punctuation">:</span><span class="literal string single">'black'</span><span class="punctuation">,</span> <span class="literal string single">'HISPANIC'</span><span class="punctuation">:</span><span class="literal string single">'hispanic'</span><span class="punctuation">,</span> <span class="literal string single">'WHITE NON HISPANIC'</span><span class="punctuation">:</span><span class="literal string single">'white'</span><span class="punctuation">,</span> <span class="literal string single">'WHITE NON HISP'</span><span class="punctuation">:</span><span class="literal string single">'white'</span><span class="punctuation">}</span> + <span class="keyword">return</span> <span class="name">d</span><span class="punctuation">[</span><span class="name">x</span><span class="punctuation">]</span> + + +<span class="keyword">def</span> <span class="name function">file2dict</span><span class="punctuation">(</span><span class="name">fname</span><span class="punctuation">):</span> + <span class="name">d</span> <span class="operator">=</span> <span class="punctuation">{}</span> <span class="comment single"># will be a nested dictionary: e.g., d[gender] = {'asian':{'name':count}, 'black':[], 'white':[], 'hispanic':[]}</span> + <span class="name">f</span> <span class="operator">=</span> <span class="name builtin">open</span><span class="punctuation">(</span><span class="name">fname</span><span class="punctuation">)</span> + <span class="name">lines</span> <span class="operator">=</span> <span class="name">f</span><span class="operator">.</span><span class="name">readlines</span><span class="punctuation">()</span> + <span class="keyword">for</span> <span class="name">line</span> <span class="operator word">in</span> <span class="name">lines</span><span class="punctuation">[</span><span class="literal number integer">1</span><span class="punctuation">:]:</span> + <span class="name">line</span> <span class="operator">=</span> <span class="name">line</span><span class="operator">.</span><span class="name">strip</span><span class="punctuation">()</span> + <span class="name">lst</span> <span class="operator">=</span> <span class="name">line</span><span class="operator">.</span><span class="name">split</span><span class="punctuation">(</span><span class="literal string single">','</span><span class="punctuation">)</span> + <span class="name">gender</span> <span class="operator">=</span> <span class="name builtin">map</span><span class="punctuation">(</span><span class="name">lst</span><span class="punctuation">[</span><span class="literal number integer">1</span><span class="punctuation">])</span> + <span class="name">ethnicity</span> <span class="operator">=</span> <span class="name builtin">map</span><span class="punctuation">(</span><span class="name">lst</span><span class="punctuation">[</span><span class="literal number integer">2</span><span class="punctuation">])</span> + <span class="name">firstname</span> <span class="operator">=</span> <span class="name">lst</span><span class="punctuation">[</span><span class="literal number integer">3</span><span class="punctuation">]</span><span class="operator">.</span><span class="name">title</span><span class="punctuation">()</span> + <span class="name">count</span> <span class="operator">=</span> <span class="name builtin">int</span><span class="punctuation">(</span><span class="name">lst</span><span class="punctuation">[</span><span class="literal number integer">4</span><span class="punctuation">])</span> + <span class="keyword">if</span> <span class="operator word">not</span> <span class="name">gender</span> <span class="operator word">in</span> <span class="name">d</span><span class="punctuation">:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="punctuation">{</span><span class="name">ethnicity</span><span class="punctuation">:</span> <span class="punctuation">{</span><span class="name">firstname</span><span class="punctuation">:</span><span class="name">count</span><span class="punctuation">}}</span> + <span class="keyword">else</span><span class="punctuation">:</span> + <span class="keyword">if</span> <span class="operator word">not</span> <span class="name">ethnicity</span> <span class="operator word">in</span> <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">]:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">][</span><span class="name">ethnicity</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="punctuation">{</span><span class="name">firstname</span><span class="punctuation">:</span><span class="name">count</span><span class="punctuation">}</span> + <span class="keyword">else</span><span class="punctuation">:</span> + <span class="keyword">if</span> <span class="operator word">not</span> <span class="name">firstname</span> <span class="operator word">in</span> <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">][</span><span class="name">ethnicity</span><span class="punctuation">]:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">][</span><span class="name">ethnicity</span><span class="punctuation">][</span><span class="name">firstname</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="name">count</span> + <span class="keyword">else</span><span class="punctuation">:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">][</span><span class="name">ethnicity</span><span class="punctuation">][</span><span class="name">firstname</span><span class="punctuation">]</span> <span class="operator">+=</span> <span class="name">count</span> + <span class="name">f</span><span class="operator">.</span><span class="name">close</span><span class="punctuation">()</span> + <span class="keyword">return</span> <span class="name">d</span> + + +<span class="keyword">def</span> <span class="name function">get_commandline_parameter</span><span class="punctuation">(</span><span class="name">lst</span><span class="punctuation">):</span> + <span class="name">d</span> <span class="operator">=</span> <span class="punctuation">{</span><span class="literal string single">'gender'</span><span class="punctuation">:</span><span class="literal string single">''</span><span class="punctuation">,</span> <span class="literal string single">'ethnicity'</span><span class="punctuation">:</span><span class="literal string single">''</span><span class="punctuation">,</span> <span class="literal string single">'top'</span><span class="punctuation">:</span><span class="literal number integer">1</span><span class="punctuation">}</span> + <span class="keyword">for</span> <span class="name">x</span> <span class="operator word">in</span> <span class="name">lst</span><span class="punctuation">:</span> + <span class="name">o</span> <span class="operator">=</span> <span class="name">x</span><span class="operator">.</span><span class="name">lower</span><span class="punctuation">()</span> + <span class="keyword">if</span> <span class="name">o</span> <span class="operator word">in</span> <span class="punctuation">[</span><span class="literal string single">'asian'</span><span class="punctuation">,</span> <span class="literal string single">'black'</span><span class="punctuation">,</span> <span class="literal string single">'white'</span><span class="punctuation">,</span> <span class="literal string single">'hispanic'</span><span class="punctuation">]:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="literal string single">'ethnicity'</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="name">o</span> + <span class="keyword">elif</span> <span class="name">o</span> <span class="operator word">in</span> <span class="punctuation">[</span><span class="literal string single">'girl'</span><span class="punctuation">,</span> <span class="literal string single">'boy'</span><span class="punctuation">]:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="literal string single">'gender'</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="name">o</span> + <span class="keyword">elif</span> <span class="name">o</span> <span class="operator">==</span> <span class="literal string single">'top'</span><span class="punctuation">:</span> + <span class="keyword">pass</span> <span class="comment single"># use default value 1</span> + <span class="keyword">elif</span> <span class="literal string single">'top'</span> <span class="operator word">in</span> <span class="name">o</span><span class="punctuation">:</span> + <span class="name">d</span><span class="punctuation">[</span><span class="literal string single">'top'</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="name builtin">int</span><span class="punctuation">(</span><span class="name">o</span><span class="punctuation">[</span><span class="literal number integer">3</span><span class="punctuation">:])</span> + <span class="keyword">else</span><span class="punctuation">:</span> + <span class="keyword">raise</span> <span class="name exception">Exception</span><span class="punctuation">(</span><span class="literal string single">'Not recognised option </span><span class="literal string interpol">%s</span><span class="literal string single">'</span> <span class="operator">%</span> <span class="punctuation">(</span><span class="name">x</span><span class="punctuation">))</span> + <span class="keyword">return</span> <span class="name">d</span> + + +<span class="keyword">def</span> <span class="name function">sort_by_value</span><span class="punctuation">(</span><span class="name">d</span><span class="punctuation">):</span> + <span class="literal string doc">''' Return a sorted list of tuples, each tuple containing a key and a value. + Note that the tuples are order in descending order of the value.'''</span> + <span class="keyword namespace">import</span> <span class="name namespace">operator</span> + <span class="name">lst</span> <span class="operator">=</span> <span class="name builtin">sorted</span><span class="punctuation">(</span><span class="name">d</span><span class="operator">.</span><span class="name">items</span><span class="punctuation">(),</span> <span class="name">key</span><span class="operator">=</span><span class="name">operator</span><span class="operator">.</span><span class="name">itemgetter</span><span class="punctuation">(</span><span class="literal number integer">1</span><span class="punctuation">),</span> <span class="name">reverse</span><span class="operator">=</span><span class="name builtin pseudo">True</span><span class="punctuation">)</span> + <span class="keyword">return</span> <span class="name">lst</span> + + +<span class="keyword namespace">import</span> <span class="name namespace">sys</span> +<span class="keyword">if</span> <span class="name variable magic">__name__</span> <span class="operator">==</span> <span class="literal string single">'__main__'</span><span class="punctuation">:</span> + <span class="name">d</span> <span class="operator">=</span> <span class="name">file2dict</span><span class="punctuation">(</span><span class="literal string single">'Popular_Baby_Names.csv'</span><span class="punctuation">)</span> + <span class="name">args</span> <span class="operator">=</span> <span class="name">get_commandline_parameter</span><span class="punctuation">(</span><span class="name">sys</span><span class="operator">.</span><span class="name">argv</span><span class="punctuation">[</span><span class="literal number integer">1</span><span class="punctuation">:])</span> + <span class="name">gender</span> <span class="operator">=</span> <span class="name">args</span><span class="punctuation">[</span><span class="literal string single">'gender'</span><span class="punctuation">]</span> + <span class="name">ethnicity</span> <span class="operator">=</span> <span class="name">args</span><span class="punctuation">[</span><span class="literal string single">'ethnicity'</span><span class="punctuation">]</span> + <span class="name">top</span> <span class="operator">=</span> <span class="name">args</span><span class="punctuation">[</span><span class="literal string single">'top'</span><span class="punctuation">]</span> + <span class="name">d2</span> <span class="operator">=</span> <span class="name">d</span><span class="punctuation">[</span><span class="name">gender</span><span class="punctuation">][</span><span class="name">ethnicity</span><span class="punctuation">]</span> + <span class="name">lst</span> <span class="operator">=</span> <span class="name">sort_by_value</span><span class="punctuation">(</span><span class="name">d2</span><span class="punctuation">)</span> + <span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name">top</span><span class="punctuation">):</span> + <span class="keyword">print</span><span class="punctuation">(</span><span class="name">lst</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">][</span><span class="literal number integer">0</span><span class="punctuation">])</span> +</pre> +</div> +<div class="section" id="id18"> +<h1><a class="toc-backref" href="#id55">排序</a></h1> <p>排序是常见重要的操作。 按照成绩排序。 按照文件名排序。 按照文件大小排序。 按照时间排序。</p> <p>Python自带的 <tt class="docutils literal">sorted</tt> 可以很好满足排序需求。</p> -<div class="section" id="id18"> -<h2><a class="toc-backref" href="#id54">排序一组数或一组字符串</a></h2> +<div class="section" id="id19"> +<h2><a class="toc-backref" href="#id56">排序一组数或一组字符串</a></h2> <p>如果需要从大到小排序， 添加 <tt class="docutils literal">reverse=True</tt> 。</p> <pre class="code python literal-block"> <span class="comment single"># Sort numbers</span> @@ -1381,13 +1470,16 @@ error-prone（易错）</p> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">sa_decr</span><span class="punctuation">)</span> </pre> </div> -<div class="section" id="id19"> -<h2><a class="toc-backref" href="#id55">自定义排序算法</a></h2> -<p>为了弄清排序的原理， 我们看两种排序算法。</p> <div class="section" id="id20"> -<h3><a class="toc-backref" href="#id56">选择排序</a></h3> +<h2><a class="toc-backref" href="#id57">自定义排序算法</a></h2> +<p>为了弄清排序的原理， 我们看两种排序算法。</p> +<div class="section" id="id21"> +<h3><a class="toc-backref" href="#id58">选择排序</a></h3> <p>遍历列表，每次把最小的那个放到最左边位置。</p> <pre class="code python literal-block"> +<span class="comment single"># Copyright (C) 2019 Hui Lan</span> +<span class="comment single"># lanhui AT zjnu.edu.cn</span> + <span class="keyword">def</span> <span class="name function">swap</span><span class="punctuation">(</span><span class="name">L</span><span class="punctuation">,</span> <span class="name">i</span><span class="punctuation">,</span> <span class="name">j</span><span class="punctuation">):</span> <span class="name">L</span><span class="punctuation">[</span><span class="name">j</span><span class="punctuation">],</span> <span class="name">L</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span> <span class="operator">=</span> <span class="name">L</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">],</span> <span class="name">L</span><span class="punctuation">[</span><span class="name">j</span><span class="punctuation">]</span> @@ -1418,9 +1510,12 @@ error-prone（易错）</p> </pre> </div> <div class="section" id="merge-sort"> -<h3><a class="toc-backref" href="#id57">合并排序 （Merge sort）</a></h3> +<h3><a class="toc-backref" href="#id59">合并排序 （Merge sort）</a></h3> <p>将列表一分为二，对每半部分排序，把排好序的两部分合并之（确保合并后同样是排好序的）。 注意到，以下的实现方式是递归。</p> <pre class="code python literal-block"> +<span class="comment single"># Copyright (C) 2019 Hui Lan</span> +<span class="comment single"># lanhui AT zjnu.edu.cn</span> + <span class="keyword">def</span> <span class="name function">_merge</span><span class="punctuation">(</span><span class="name">L</span><span class="punctuation">,</span> <span class="name">R</span><span class="punctuation">):</span> <span class="literal string doc">''' Return a sorted list that combines the sorted list L and sorted list R.'''</span> <span class="name">nL</span> <span class="operator">=</span> <span class="name builtin">len</span><span class="punctuation">(</span><span class="name">L</span><span class="punctuation">)</span> @@ -1463,8 +1558,8 @@ error-prone（易错）</p> </pre> </div> </div> -<div class="section" id="id21"> -<h2><a class="toc-backref" href="#id58">比较排序速度</a></h2> +<div class="section" id="id22"> +<h2><a class="toc-backref" href="#id60">比较排序速度</a></h2> <p>排序是 Python 的核心算法，所以是优化了再优化。</p> <p>Python 自带的排序算法最快， <tt class="docutils literal">selection_sort</tt> 最慢。</p> <pre class="code python literal-block"> @@ -1490,7 +1585,7 @@ error-prone（易错）</p> <span class="name">result2</span> <span class="operator">=</span> <span class="name">selection_sort</span><span class="punctuation">(</span><span class="name">L</span><span class="punctuation">)</span> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">time</span><span class="operator">.</span><span class="name">time</span><span class="punctuation">()</span> <span class="operator">-</span> <span class="name">now</span><span class="punctuation">)</span> -<span class="keyword">assert</span> <span class="name">result0</span><span class="operator">==</span> <span class="name">result1</span> +<span class="keyword">assert</span> <span class="name">result0</span> <span class="operator">==</span> <span class="name">result1</span> <span class="keyword">assert</span> <span class="name">result1</span> <span class="operator">==</span> <span class="name">result2</span> </pre> <p>在命令行运行上面的程序，在作者的计算机上得到如下的结果。</p> @@ -1503,8 +1598,8 @@ error-prone（易错）</p> <div class="line">11.57</div> </div> </div> -<div class="section" id="id22"> -<h2><a class="toc-backref" href="#id59">排序元组列表</a></h2> +<div class="section" id="id23"> +<h2><a class="toc-backref" href="#id61">排序元组列表</a></h2> <p>一个元组由多个元素组成，多个元组组成元组列表， 如何按照某个元素进行排序呢？</p> <p>可以有以下两种方案。一种用模块 <tt class="docutils literal">operator</tt> ， 一种用 <tt class="docutils literal">lambda</tt> 函数。</p> <pre class="code python literal-block"> @@ -1534,7 +1629,7 @@ error-prone（易错）</p> </pre> </div> <div class="section" id="lambda"> -<h2><a class="toc-backref" href="#id60">巧用 lambda 函数进行灵活排序</a></h2> +<h2><a class="toc-backref" href="#id62">巧用 lambda 函数进行灵活排序</a></h2> <p>如何把一个由字符串组成的列表按照字符串的长短进行排序？</p> <pre class="code python literal-block"> <span class="name">lst</span> <span class="operator">=</span> <span class="punctuation">[</span><span class="literal string single">'this'</span><span class="punctuation">,</span> <span class="literal string single">'is'</span><span class="punctuation">,</span> <span class="literal string single">'a'</span><span class="punctuation">,</span> <span class="literal string single">'example'</span><span class="punctuation">]</span> @@ -1591,8 +1686,8 @@ What here shall miss, our toil shall strive to mend.'''</span> </div> </div> </div> -<div class="section" id="id23"> -<h1><a class="toc-backref" href="#id61">参考</a></h1> +<div class="section" id="id24"> +<h1><a class="toc-backref" href="#id63">参考</a></h1> <ul class="simple"> <li>Think Python 2e – Green Tea Press. <a class="reference external" href="http://greenteapress.com/thinkpython2/thinkpython2.pdf">http://greenteapress.com/thinkpython2/thinkpython2.pdf</a>.</li> </ul> |