python 解释器交互模块 -- sys

sys模块是与python解释器交互的一个接口

sys.argv 命令行参数List，第一个元素是程序本身路径
sys.getdefaultencoding(): 获取系统当前编码，一般默认为ascii。
sys.setdefaultencoding(): 设置系统默认编码，执行dir（sys）时不会看到这个方法，在解释器中执行不通过，可以先执行reload(sys)，在执行 setdefaultencoding('utf8')，此时将系统默认编码设置为utf8。（见设置系统默认编码 ）。
sys.getfilesystemencoding(): 获取文件系统使用编码方式，Windows下返回'mbcs'，mac下返回'utf-8'.
sys.modules.keys() 返回所有已经导入的模块列表
sys.exc_info() 获取当前正在处理的异常类,exc_type、exc_value、exc_traceback当前处理的异常详细信息
sys.exit(n) 退出程序，正常退出时exit(0)
sys.hexversion 获取Python解释程序的版本值，16进制格式如：0x020403F0
sys.version 获取Python解释程序的版本信息
sys.maxint 最大的Int值
sys.maxunicode 最大的Unicode值
sys.modules 返回系统导入的模块字段，key是模块名，value是模块
sys.path 返回模块的搜索路径，初始化时使用PYTHONPATH环境变量的值
sys.platform 返回操作系统平台名称
sys.stdout 标准输出
sys.stdin 标准输入
sys.stderr 错误输出
sys.exc_clear() 用来清除当前线程所出现的当前的或最近的错误信息
sys.exec_prefix 返回平台独立的python文件安装的位置
sys.byteorder 本地字节规则的指示器，big-endian平台的值是'big',little-endian平台的值是'little'
sys.copyright 记录python版权相关的东西
sys.api_version 解释器的C的API版本

1,argv : 处理命令行参数

在解释器启动后, argv 列表包含了传递给脚本的所有参数, 列表的第一个元素为脚本自身的名称.

import sys
print(sys.argv[0])

结果:D:/pythonfile/PyCharm/week6/da.py

2,path : 处理模块

path 列表是一个由目录名构成的列表, Python 从中查找扩展模块( Python 源模块, 编译模块,或者二进制扩展).

启动 Python 时,这个列表从根据内建规则, PYTHONPATH 环境变量的内容, 以及注册表( Windows 系统)等进行初始化.

由于它只是一个普通的列表, 你可以在程序中对它进行操作,

import sys

print(sys.path)

结果 : ['D:\pythonfile\PyCharm\week6', 'D:\pythonfile\PyCharm', 'D:\pythonfile\PyCharm\venv\Scripts\python37.zip', 'C:\python37\Lib', 'C:\python37\DLLs', "C:\Users\deng'peng\AppData\Local\Programs\Python\Python37-32", 'D:\pythonfile\PyCharm\venv', 'D:\pythonfile\PyCharm\venv\lib\site-packages', 'D:\pythonfile\PyCharm\venv\lib\site-packages\setuptools-39.1.0-py3.7.egg', 'D:\pythonfile\PyCharm\venv\lib\site-packages\pip-10.0.1-py3.7.egg', 'D:\软件\PyCharm 2018.1.4\helpers\pycharm_matplotlib_backend']

3,modules : 查找已导入的模块

全局字典，每当python启动时该字段自动加载到内存中。新加模块sys.modules会自动记录该模块，第二次导入时直接从字典中加载，加快运行速度。他拥有字典的一切方法。
keys是模块名
values是模块
modules返回路径

import sys


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

运行结果:
{'sys': <module 'sys' (built-in)>, 'builtins': <module 'builtins' (built-in)>, '_frozen_importlib': <module '_frozen_importlib' (frozen)>, '_imp': <module '_imp' (built-in)>, '_thread': <module '_thread' (built-in)>, '_warnings': <module '_warnings' (built-in)>, '_weakref': <module '_weakref' (built-in)>, 'zipimport': <module 'zipimport' (built-in)>, '_frozen_importlib_external': <module '_frozen_importlib_external' (frozen)>, '_io': <module 'io' (built-in)>, 'marshal': <module 'marshal' (built-in)>, 'nt': <module 'nt' (built-in)>, 'winreg': <module 'winreg' (built-in)>, 'encodings': <module 'encodings' from 'C:\python37\Lib\encodings\__init__.py'>, 'codecs': <module 'codecs' from 'C:\python37\Lib\codecs.py'>, '_codecs': <module '_codecs' (built-in)>, 'encodings.aliases': <module 'encodings.aliases' from 'C:\python37\Lib\encodings\aliases.py'>, 'encodings.utf_8': <module 'encodings.utf_8' from 'C:\python37\Lib\encodings\utf_8.py'>, '_signal': <module '_signal' (built-in)>, '__main__': <module '__main__' from 'D:/pythonfile/PyCharm/week6/day34.py'>, 'encodings.latin_1': <module 'encodings.latin_1' from 'C:\python37\Lib\encodings\latin_1.py'>, 'io': <module 'io' from 'C:\python37\Lib\io.py'>, 'abc': <module 'abc' from 'C:\python37\Lib\abc.py'>, '_abc': <module '_abc' (built-in)>, 'site': <module 'site' from 'C:\python37\Lib\site.py'>, 'os': <module 'os' from 'C:\python37\Lib\os.py'>, 'stat': <module 'stat' from 'C:\python37\Lib\stat.py'>, '_stat': <module '_stat' (built-in)>, 'ntpath': <module 'ntpath' from 'C:\python37\Lib\ntpath.py'>, 'genericpath': <module 'genericpath' from 'C:\python37\Lib\genericpath.py'>, 'os.path': <module 'ntpath' from 'C:\python37\Lib\ntpath.py'>, '_collections_abc': <module '_collections_abc' from 'C:\python37\Lib\_collections_abc.py'>, '_sitebuiltins': <module '_sitebuiltins' from 'C:\python37\Lib\_sitebuiltins.py'>, '_bootlocale': <module '_bootlocale' from 'C:\python37\Lib\_bootlocale.py'>, '_locale': <module '_locale' (built-in)>, 'encodings.gbk': <module 'encodings.gbk' from 'C:\python37\Lib\encodings\gbk.py'>, '_codecs_cn': <module '_codecs_cn' (built-in)>, '_multibytecodec': <module '_multibytecodec' (built-in)>, 'encodings.cp437': <module 'encodings.cp437' from 'C:\python37\Lib\encodings\cp437.py'>, 'sitecustomize': <module 'sitecustomize' from 'D:\软件\PyCharm 2018.1.4\helpers\pycharm_matplotlib_backend\sitecustomize.py'>, 'time': <module 'time' (built-in)>, 'random': <module 'random' from 'C:\python37\Lib\random.py'>, 'warnings': <module 'warnings' from 'C:\python37\Lib\warnings.py'>, 'types': <module 'types' from 'C:\python37\Lib\types.py'>, 'math': <module 'math' (built-in)>, 'hashlib': <module 'hashlib' from 'C:\python37\Lib\hashlib.py'>, '_hashlib': <module '_hashlib' from 'C:\python37\DLLs\_hashlib.pyd'>, '_blake2': <module '_blake2' (built-in)>, '_sha3': <module '_sha3' (built-in)>, 'itertools': <module 'itertools' (built-in)>, 'bisect': <module 'bisect' from 'C:\python37\Lib\bisect.py'>, '_bisect': <module '_bisect' (built-in)>, '_random': <module '_random' (built-in)>}
``````````````
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', 'time', 'random', 'warnings', 'types', 'math', 'hashlib', '_hashlib', '_blake2', '_sha3', 'itertools', 'bisect', '_bisect', '_random'])
``````````````
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 'C:\python37\Lib\encodings\__init__.py'>, <module 'codecs' from 'C:\python37\Lib\codecs.py'>, <module '_codecs' (built-in)>, <module 'encodings.aliases' from 'C:\python37\Lib\encodings\aliases.py'>, <module 'encodings.utf_8' from 'C:\python37\Lib\encodings\utf_8.py'>, <module '_signal' (built-in)>, <module '__main__' from 'D:/pythonfile/PyCharm/week6/day34.py'>, <module 'encodings.latin_1' from 'C:\python37\Lib\encodings\latin_1.py'>, <module 'io' from 'C:\python37\Lib\io.py'>, <module 'abc' from 'C:\python37\Lib\abc.py'>, <module '_abc' (built-in)>, <module 'site' from 'C:\python37\Lib\site.py'>, <module 'os' from 'C:\python37\Lib\os.py'>, <module 'stat' from 'C:\python37\Lib\stat.py'>, <module '_stat' (built-in)>, <module 'ntpath' from 'C:\python37\Lib\ntpath.py'>, <module 'genericpath' from 'C:\python37\Lib\genericpath.py'>, <module 'ntpath' from 'C:\python37\Lib\ntpath.py'>, <module '_collections_abc' from 'C:\python37\Lib\_collections_abc.py'>, <module '_sitebuiltins' from 'C:\python37\Lib\_sitebuiltins.py'>, <module '_bootlocale' from 'C:\python37\Lib\_bootlocale.py'>, <module '_locale' (built-in)>, <module 'encodings.gbk' from 'C:\python37\Lib\encodings\gbk.py'>, <module '_codecs_cn' (built-in)>, <module '_multibytecodec' (built-in)>, <module 'encodings.cp437' from 'C:\python37\Lib\encodings\cp437.py'>, <module 'sitecustomize' from 'D:\软件\PyCharm 2018.1.4\helpers\pycharm_matplotlib_backend\sitecustomize.py'>, <module 'time' (built-in)>, <module 'random' from 'C:\python37\Lib\random.py'>, <module 'warnings' from 'C:\python37\Lib\warnings.py'>, <module 'types' from 'C:\python37\Lib\types.py'>, <module 'math' (built-in)>, <module 'hashlib' from 'C:\python37\Lib\hashlib.py'>, <module '_hashlib' from 'C:\python37\DLLs\_hashlib.pyd'>, <module '_blake2' (built-in)>, <module '_sha3' (built-in)>, <module 'itertools' (built-in)>, <module 'bisect' from 'C:\python37\Lib\bisect.py'>, <module '_bisect' (built-in)>, <module '_random' (built-in)>])
```````````````````
<module 'os' from 'C:\python37\Lib\os.py'>

4,platform : 获得当前平台

sys.platform  返回当前平台 出现如： "win32" "linux2" 等

print(sys.platform)

结果:win32

5,exit : 退出程序

如果准备在退出前自己清理一些东西(比如删除临时文件), 你可以配置一个 "退出处理函数"(exit handler), 它将在程序退出的时候自动被调用

import sys
print("hello")
try:
    sys.exit(1)
except SystemExit: # 捕获退出的异常
    pass           # 捕获后不做任何操作
print("There")

结果:
hello
There