Pythone3 sys模块

1.sys.argv 可以实现从程序外部向程序传递参数
2.sys.exit() 程序中间退出，exit(0)正常退出，其他为异常退出
3.sys.getdefaultencoding() 获取系统编码方式
4.sys.setdefaultencoding() 设置系统编码方式
5.sys.getfilesystemencoding() 获取文件系统编码方式
6.sys.path 获取系统环境变量中PATH的路径字符串
7.sys.path.append("路径") 追加路径到系统环境变量PATH的后面
8.sys.path.insert("路径") 将路径插入到系统环境变量PATH的最前面
9.sys.platform: 获取当前系统平台。
10.sys.modules 是一个全局字典，该字典是python启动后就加载在内存中。每当程序员导入新的模块，sys.modules将自动记录该模块。当第二次再导入该模块时，python会直接到字典中查找，从而加快了程序运行的速度。它拥有字典所拥有的一切方法。

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print(sys.modules.keys()) print(sys.modules.values()) print(sys.modules["os"])

输出结果：

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dict_keys(['sys', 'builtins', '_frozen_importlib', '_imp', '_thread', '_warnings', '_weakref', 'zipimport', '_frozen_importlib_external', '_io', 'marshal', 'nt', 'winreg', 'encodings', 'codecs', '_codecs', 'encodings.aliases', 'encodings.utf_8', '_signal', '__main__', 'encodings.latin_1', 'io', 'abc', '_abc', 'site', 'os', 'stat', '_stat', 'ntpath', 'genericpath', 'os.path', '_collections_abc', '_sitebuiltins', '_bootlocale', '_locale', 'encodings.gbk', '_codecs_cn', '_multibytecodec', 'encodings.cp437', 'sitecustomize']) dict_values([<module 'sys' (built-in)>, <module 'builtins' (built-in)>, <module '_frozen_importlib' (frozen)>, <module '_imp' (built-in)>, <module '_thread' (built-in)>, <module '_warnings' (built-in)>, <module '_weakref' (built-in)>, <module 'zipimport' (built-in)>, <module '_frozen_importlib_external' (frozen)>, <module 'io' (built-in)>, <module 'marshal' (built-in)>, <module 'nt' (built-in)>, <module 'winreg' (built-in)>, <module 'encodings' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\__init__.py'>, <module 'codecs' from 'D:\\Programs\\Python\\Python37\\lib\\codecs.py'>, <module '_codecs' (built-in)>, <module 'encodings.aliases' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\aliases.py'>, <module 'encodings.utf_8' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\utf_8.py'>, <module '_signal' (built-in)>, <module '__main__' from 'D:/Programs/Python/PycharmProjects/OldManS14/day05/module/sys_模块.py'>, <module 'encodings.latin_1' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\latin_1.py'>, <module 'io' from 'D:\\Programs\\Python\\Python37\\lib\\io.py'>, <module 'abc' from 'D:\\Programs\\Python\\Python37\\lib\\abc.py'>, <module '_abc' (built-in)>, <module 'site' from 'D:\\Programs\\Python\\Python37\\lib\\site.py'>, <module 'os' from 'D:\\Programs\\Python\\Python37\\lib\\os.py'>, <module 'stat' from 'D:\\Programs\\Python\\Python37\\lib\\stat.py'>, <module '_stat' (built-in)>, <module 'ntpath' from 'D:\\Programs\\Python\\Python37\\lib\\ntpath.py'>, <module 'genericpath' from 'D:\\Programs\\Python\\Python37\\lib\\genericpath.py'>, <module 'ntpath' from 'D:\\Programs\\Python\\Python37\\lib\\ntpath.py'>, <module '_collections_abc' from 'D:\\Programs\\Python\\Python37\\lib\\_collections_abc.py'>, <module '_sitebuiltins' from 'D:\\Programs\\Python\\Python37\\lib\\_sitebuiltins.py'>, <module '_bootlocale' from 'D:\\Programs\\Python\\Python37\\lib\\_bootlocale.py'>, <module '_locale' (built-in)>, <module 'encodings.gbk' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\gbk.py'>, <module '_codecs_cn' (built-in)>, <module '_multibytecodec' (built-in)>, <module 'encodings.cp437' from 'D:\\Programs\\Python\\Python37\\lib\\encodings\\cp437.py'>, <module 'sitecustomize' from 'D:\\Programs\\Python\\PyCharm 2018.1.4\\helpers\\pycharm_matplotlib_backend\\sitecustomize.py'>]) <module 'os' from 'D:\\Programs\\Python\\Python37\\lib\\os.py'>

11. stdin , stdout , 以及stderr 变量包含与标准I/O 流对应的流对象. 如果需要更好地控制输出,,而print 不能满足你的要求, 它们就是你所需要的. 你也可以替换它们, 这时候你就可以重定向输出和输入到其它设备( device ), 或者以非标准的方式处理它们

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sys.stderr.write("stderr") print("=======") sys.stdout.write("stdout")

输出结果：

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1 2	stderr======= stdout