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关于\n\n`__name__`,`__main__.py`&`__init__.py`\n\n * 当脚本作为单个文件直接运行是，`__name__`为`'__main__'`\n\n * 当脚本作为模块导入使用时，`__name__`为这个模块的名字\n\n`if __name__ == '__main__'`则表示当前脚本直接执行，而非被其他模块调用时，运行后面的代码。\n\n> 这为测试驱动开发提供了极好的支持，我们可以在每个模块中写上测试代码，这些测试代码仅当模块被Python直接执行时才会运行，代码和测试完美的结合在一起。\n\n假设有如下一个包\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n> 关于`__init__.py`\n> 如果目录中包含了 `__init__.py` 时，当用 import 导入该目录时，会执行 `__init__.py` 里面的代码。\n\n目录中所有 py 文件的内容都为：\n\n`print(__name__)`\n\n在a文件夹的父文件夹中\n\n * 执行命令：python -c “import a.b.c”，输出结果：\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n作为模块导入，`__name__`为这个模块的名字，导入时，`__init__.py`中的代码会被执行\n\n * 执行命令：python -m a.b，输出结果：\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\nb作为一个模块被执行，`__init__.py`中的代码会被执行，模块中的`__main__.py`作为入口执行，其中的`__name__`参数值为`__main__`\n\n * 执行命令：python a\\b，输出结果：\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n执行a\\b这个包，即运行a\\b这个包的`__main__.py`，不会执行`__init__.py`,其中`__main__.py`的`__name__`参数值为`__main__`\n\n### 关于sys.path\n\nsys.path中的第一个元素为当前工作路径。\n脚本作为一个模块运行时，即执行`python -m package`，sys.path的第一个参数为执行命令行的路径。当直接执行脚本时，sys.path的第一个参数为相应脚本的路径。\n\n### 类与self\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n![Alt text](assets/1608718131552.png)\n\n## 命令行参数\n\n * `-c command` \\- 执行 command 中的 Python 代码。\n\n * `-m ` \\- 在 sys.path 中搜索指定名称的模块并将其内容作为 **main** 模块来执行。\n\n使用 sys 的 sys.argv 来获取命令行参数：\nsys.argv[0] 表示脚本名，args[1:]后面的才是真正命令行输入的参数。\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n> getopt模块是专门处理命令行参数的模块，用于获取命令行选项和参数，也就是sys.argv。更多参见: \n\n## 应用\n\n### 修改文件\n\n修改某一行\n\n```cpp\nstring str1 = "test";\nstring str2 = "test";\n\n```\n\n* * *\n\n替换字符串，直接写入源文件\n\n```csharp\nstring a = "test";\nstring tmp = "est";\nstring b = "t" + tmp;\nConsole.WriteLine(string .ReferenceEquals(str1, str2));\n\n```\n\n* * *\n\n写入新文件后再替换源文件\n\n```csharp\nstring a = "test";\nstring tmp = "est";\nstring b = "t" + tmp;\nConsole.WriteLine(string .ReferenceEquals(str1, str2));\n\n```\n\n* * *\n\n正则表达式 re 的应用\n\n```csharp\nstring a = "test";\nstring tmp = "est";\nstring b = "t" + tmp;\nConsole.WriteLine(string .ReferenceEquals(str1, str2));\n\n```\n\n输出\n\n```csharp\nstring a = "test";\nstring tmp = "est";\nstring b = "t" + tmp;\nConsole.WriteLine(string .ReferenceEquals(str1, str2));\n\n```\n```csharp\nstring a = "test";\nstring tmp = "est";\nstring b = "t" + tmp;\nConsole.WriteLine(string .ReferenceEquals(str1, str2));\n\n```\n\n## Ref\n\n\n" }