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"contentMarkdown": "# 【Python】Python3基础\n\n> 创建时间：2021/5/11 15:02\n\n * 【Python】Python3基础\n * 知识结构与资料\n * 基础语法特征\n * string\n * list\n * 增删改查\n * 排序，反转，计算长度\n * 遍历，创建，计算\n * for…in\n * range\n * 计算\n * 简单的遍历并处理\n * 截取一部分\n * 元组\n * 字典\n * 遍历\n * 逻辑运算\n * 输入：\n * if-else\n * while\n * 函数\n * class\n * 导入\n * 函数导入\n * 类导入\n * 文件\n * 读取整个文件\n * 逐行读取\n * 写入文件\n * json\n * 异常\n * python3与python2的区别\n * 除法\n * 进阶\n * arbitrary number of arguments\n * **kwargs\n * os.system & os.popen & subprocess\n * os.system\n * os.popen\n * subprocess.Popen\n * 对比\n * Lambda\n * Map\n * filter\n * Iterator & Generator\n * Iterator\n * Generator\n * Building Generators With Generator Expressions\n * 深入理解\n * Profiling Generator Performance\n * 工具与应用\n * Sublime Build Python\n * Ref\n\n## 知识结构与资料\n\n\n\n\n\n\n\n\n快速教程：\n\n\n\n## 基础语法特征\n\n### string\n\n用引号括起的都是字符串\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n加号(+)来合并字符串\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\ntitle() - 将每个单词的首字母都改为大写。\nupper()、lower()\n\nrstrip() 删除右侧空白\nlstrip() 删除左侧空白\nstrip() 删除两端空白\nstrip() 不改变原来的字符串\n\nstr() - 将数字转换为字符串再进行拼接\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### list\n\n方括号([])来表示列表，并用逗号来分隔其中的元素\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### 增删改查\n\n修改元素直接用索引修改\n\n在末尾添加：append\n\n插入：insert\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\ndel：按索引删除\npop()：删除列表最后一个元素并返回最后一个元素的值。\npop(index) - 传索引删除任意位置的值并返回\nremove()：按值删除第一个元素\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n> list[-2] 是获取倒数第二个元素\n\n#### 排序，反转，计算长度\n\n改变原列表：\nlist.sort()\nlist.sort(reverse=True) - 反转\n\n不影响原始排列顺序：\nsorted(list)\nsorted(list, reverse=True)\n\nlist.reverse()\n\nlen(list)\n\n#### 遍历，创建，计算\n\n##### for…in\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n##### range\n\nrange(1,6) - 前闭后开\n\nrange(0,11,2) - 指定步长为2\n\n##### 计算\n\nmin()：计算最小值\nmax()：计算最大值\nsum()：计算总和\n\n##### 简单的遍历并处理\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n##### 截取一部分\n\n前闭后开\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n如果使用 names3=names，则只是把引用（地址）赋值过去，指向的是用一份数据。\n\n### 元组\n\n不可变的列表被称为元组\n圆括号标识\n访问和遍历方式与列表一致\n\n### 字典\n\n可将任何Python对象用作字典中的值\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### 遍历\n\n遍历所有键值对\nitems()\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n遍历所有键\nfor k in cats.keys()\nfor k in cats\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n没有顺序\n\n遍历所有值 values()\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n遍历并去除重复项 set()\nfor value in set(cat.values())\n\n> 可以在列表中嵌套字典、在字典中嵌套列表以及在字典中嵌套字典。\n\n### 逻辑运算\n\n * and\n\n * or\n\n * in - 判断列表是否包含某元素\n\n * not in - 判断不包含\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### 输入：\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### if-else\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### while\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\nfor…in\nelse\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\npass 不做任何事情，一般用做占位语句\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### 函数\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n传递任意数量的实参\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n * 函数名应只包含小写字母和下划线\n\n * 给形参指定默认值时，等号两边不要有空格\n\n### class\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### 导入\n\n#### 函数导入\n\n> cat.py\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\nimport cat\nimport cat as c\n\nfrom cat import eat, run\nfrom cat import eat as cat_eat\n\nfrom cat import * #不推荐。避免同名函数覆盖\n\n要么只导入你需要使用的函数，要么导入整个模块并使用句点表示法。\n\n#### 类导入\n\n假如 car.py 包含了三个类 Car ， Battery 和 ElectricCar 。\n\nimport car\nfrom car import Car, ElectricCar\nfrom module_name import * #不推荐\n\n### 文件\n\nwith - 在不再需要访问文件后将其关闭。有了 with 你只管打开文件，并在需要时使用它，Python自会 在合适的时候自动将其关闭。\nopen() - 用于打开一个文件，参数为文件的路径。文件路径可以是相对路径，也可以是绝对路径。\n\n#### 读取整个文件\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n> 相比于原始文件，该输出唯一不同的地方是末尾多了一个空行。为何会多出这个空行呢?因为 read() 到达文件末尾时返回一个空字符串，而将这个空字符串显示出来时就是一个空行。要删除多出来的空行，可在print语句中使用 rstrip()。\n\n#### 逐行读取\n\n要以每次一行的方式检查文件，可对文件对象使用for循环。\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### 写入文件\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n * r ：只读。\n\n * w : 只写。如果文件不存在则创建，如果文件存在则先清空，再写入。\n\n * a ：附加模式，写入的内容追加到原始文件后面。如果文件不存在则创建。\n\n * r+ ：可读可写。\n\n#### json\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### 异常\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n## python3与python2的区别\n\n### 除法\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n## 进阶\n\n### arbitrary number of arguments\n\nThe **non keyword arguments** are passed as a tuple and these passed arguments make tuple inside the function with same name as the parameter excluding asterisk `*`.\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### **kwargs\n\nThe arguments are passed as a dictionary\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### os.system & os.popen & subprocess\n\n#### os.system\n\n**同步调用（阻塞）**\n\n * os.system方法是os模块最基础的方法，其它的方法一般在该方法基础上封装完成。\n\n * 创建一个子进程在系统上执行命令行，子进程的执行结果无法影响主进程。\n\n * 返回值是脚本的退出状态码，0表示成功，其他均为失败\n\n坑点：\n\n 1. 连续几个system命令执行，是启动了多个子进程来运行，上一条 cd 的效果不会在下一个子进程中生效。\n\n\n\n 2. os.system(command) 在调用完shell脚本后，返回一个16位的二进制数，低位为杀死所调用脚本的信号号码，高位为脚本的退出状态码，即脚本中“exit 1”的代码执行后，os.system函数返回值的高位数则是1，如果低位数是0的情况下，则函数的返回值是0x0100,换算为十进制得到256。\n\n#### os.popen\n\n**非阻塞**\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\ncommand – 使用的命令。\nmode – 模式权限可以是 ‘r’(默认) 或 ‘w’。\nbufsize – 指明了文件需要的缓冲大小：0意味着无缓冲；1意味着行缓冲；\n\n返回一个文件描述符号为fd的打开的文件对象。\n\n**read()、eadlines()、close()** 会产生阻塞效果。\n**文件用完就应该关闭** 。使用如下方法会自动关闭\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n像调用”ls”这样的shell命令，应该使用popen的方法来获得内容，对比如下：\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### subprocess.Popen\n\n可以用 **wait** 来等待命令执行完成\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n当test.txt大于64k时，会阻塞住。原因是，子进程产生一些数据，他们会被buffer起来，当buffer满了，会写到子进程的标准输出和标准错误输出，这些东西通过管道发送给父进程。当管道满了之后，子进程就停止写入，于是就卡住了。\n\n解决方法：\n\n 1. 在wait前，读取管道，这样管道就不会满\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n 2. 使用communicate\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### 对比\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### Lambda\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### Map\n\n将函数应用于各种数据结构中的元素\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### filter\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n### Iterator & Generator\n\n#### Iterator\n\nAn iterator is an object that can be iterated upon, meaning that you can traverse through all the values.\n\n**Iterator vs Iterable：** Lists, tuples, dictionaries, and sets are all iterable objects. They are iterable containers which you can get an iterator from.\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\nLooping Through an Iterator: We can also use a for loop to iterate through an iterable object.\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\nCreate an Iterator\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### Generator\n\n在 Python 中，使用了 yield 的函数被称为生成器函数（generator functions）。\nIntroduced with PEP 255, generator functions are a special kind of function that return **a lazy iterator**. These are objects that you can loop over like a list. However, unlike lists, lazy iterators **do not store their contents in memory**.\n\n在调用生成器运行的过程中，每次遇到 yield 时函数会暂停并保存当前所有的运行信息，返回 yield 的值, 并在下一次执行 next() 方法时从当前位置继续运行。\n\nExample: Generating an Infinite Sequence\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n##### Building Generators With Generator Expressions\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n#### 深入理解\n\npython的yield关键字与C#类似。函数中有yield语句时，调用该函数，会返回一个迭代器，并不会真正执行该函数。首次，对该函数调用next时，函数开始执行，会尝试执行到第一次yield语句，获取返回值。如果在调用到yield语句之前，函数返回，则会抛出异常 StopIteration 。如果成功执行到yield语句并返回，再次调用next函数时，会从这个yield语句的下一个语句开始执行。\n\n示例如下，调用recv，会返回一个generator对象，调用next时，函数开始执行。而起初在调用时，会执行到break并返回，无法执行到yield，next函数会抛出异常，无法继续遍历。直到满足条件，可以执行到yield时，调用next才会获取到返回值 cnt ，下次调用next时，本次yield语句后的一个语句开始执行。\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n输出如下：\n\n\n\n#### Profiling Generator Performance\n\n```csharp\nstring str1 = String.Empty;\nstring str2 = String.Empty;\n\nstr2 = String.Intern(sb.ToString());\n\nif((object)str1==(object)str2)\n Console.WriteLine("The strings are equal.");\nelse\n Console.WriteLine("The strings are not equal.");\n\n```\n\n## 工具与应用\n\n\n\n### Sublime Build Python\n\n\n\n## Ref\n\n\n\n\n\n\n\n"
}