python：sys模块整理

Posted 2021-03-13 xmcwm

　　python的sys模块为开发者提供了访问由解释器使用或维护的接口，并提供了一些函数用来和解释器进行交互，操控python的运行环境

　　下面将介绍sys模块常用的属性和方法

1、动态对象

（1）sys.argv列表

　　功能：在程序外部（命令行）向内部传递参数；其中sys.argv[0]是脚本名称

　　脚本：test.py

import sys

print("sys.argv[0]")
print("sys.argv[1]")


>>python test.py argv
test.py
argv

（2）sys.path列表

　　功能：模块的搜索路径；sys.path[0]表示当前脚本所在目录，在交互模式下sys.path[0]为空字符；自定义脚本放在sys.path列表中的任何一个目录下就可以通过import导入使用

　　脚本：test.py

import sys

print(sys.path)


>>python test.py
[‘/box‘, ‘/usr/local/python-3.6.0/lib/python36.zip‘, ‘/usr/local/python-3.6.0/lib/python3.6‘, ‘/usr/local/python-3.6.0/lib/python3.6/lib-dynload‘, ‘/usr/local/python-3.6.0/lib/python3.6/site-packages‘]

（3）sys.modules字典

　　功能：一个全局字典，python启动后就将该字典加载到内存中，每导入一个新模块，都会被记录在这个字典中，第二次导入相同模块时，解释器将直接查找字典，从而加快程序运行的速度

　　脚本：test.py

import sys

print(sys.modules)


>>python test.py
{‘builtins‘: <module ‘builtins‘ (built-in)>, ‘sys‘: <module ‘sys‘ (built-in)>, ‘_frozen_importlib‘: <module ‘_frozen_importlib‘ (frozen)>, ‘_imp‘: <module ‘_imp‘ (built-in)>, ‘_warnings‘: <module ‘_warnings‘ (built-in)>, ‘_thread‘: <module ‘_thread‘ (built-in)>, ‘_weakref‘: <module ‘_weakref‘ (built-in)>, ‘_frozen_importlib_external‘: <module ‘_frozen_importlib_external‘ (frozen)>, ‘_io‘: <module ‘io‘ (built-in)>, ‘marshal‘: <module ‘marshal‘ (built-in)>, ‘posix‘: <module ‘posix‘ (built-in)>, ‘zipimport‘: <module ‘zipimport‘ (built-in)>, ‘encodings‘: <module ‘encodings‘ from ‘/usr/local/python-3.6.0/lib/python3.6/encodings/__init__.py‘>, ‘codecs‘: <module ‘codecs‘ from ‘/usr/local/python-3.6.0/lib/python3.6/codecs.py‘>, ‘_codecs‘: <module ‘_codecs‘ (built-in)>, ‘encodings.aliases‘: <module ‘encodings.aliases‘ from ‘/usr/local/python-3.6.0/lib/python3.6/encodings/aliases.py‘>, ‘encodings.utf_8‘: <module ‘encodings.utf_8‘ from ‘/usr/local/python-3.6.0/lib/python3.6/encodings/utf_8.py‘>, ‘_signal‘: <module ‘_signal‘ (built-in)>, ‘__main__‘: <module ‘__main__‘ from ‘main.py‘>, ‘encodings.latin_1‘: <module ‘encodings.latin_1‘ from ‘/usr/local/python-3.6.0/lib/python3.6/encodings/latin_1.py‘>, ‘io‘: <module ‘io‘ from ‘/usr/local/python-3.6.0/lib/python3.6/io.py‘>, ‘abc‘: <module ‘abc‘ from ‘/usr/local/python-3.6.0/lib/python3.6/abc.py‘>, ‘_weakrefset‘: <module ‘_weakrefset‘ from ‘/usr/local/python-3.6.0/lib/python3.6/_weakrefset.py‘>, ‘_bootlocale‘: <module ‘_bootlocale‘ from ‘/usr/local/python-3.6.0/lib/python3.6/_bootlocale.py‘>, ‘_locale‘: <module ‘_locale‘ (built-in)>, ‘site‘: <module ‘site‘ from ‘/usr/local/python-3.6.0/lib/python3.6/site.py‘>, ‘os‘: <module ‘os‘ from ‘/usr/local/python-3.6.0/lib/python3.6/os.py‘>, ‘errno‘: <module ‘errno‘ (built-in)>, ‘stat‘: <module ‘stat‘ from ‘/usr/local/python-3.6.0/lib/python3.6/stat.py‘>, ‘_stat‘: <module ‘_stat‘ (built-in)>, ‘posixpath‘: <module ‘posixpath‘ from ‘/usr/local/python-3.6.0/lib/python3.6/posixpath.py‘>, ‘genericpath‘: <module ‘genericpath‘ from ‘/usr/local/python-3.6.0/lib/python3.6/genericpath.py‘>, ‘os.path‘: <module ‘posixpath‘ from ‘/usr/local/python-3.6.0/lib/python3.6/posixpath.py‘>, ‘_collections_abc‘: <module ‘_collections_abc‘ from ‘/usr/local/python-3.6.0/lib/python3.6/_collections_abc.py‘>, ‘_sitebuiltins‘: <module ‘_sitebuiltins‘ from ‘/usr/local/python-3.6.0/lib/python3.6/_sitebuiltins.py‘>, ‘sysconfig‘: <module ‘sysconfig‘ from ‘/usr/local/python-3.6.0/lib/python3.6/sysconfig.py‘>, ‘_sysconfigdata_m_linux_x86_64-linux-gnu‘: <module ‘_sysconfigdata_m_linux_x86_64-linux-gnu‘ from ‘/usr/local/python-3.6.0/lib/python3.6/_sysconfigdata_m_linux_x86_64-linux-gnu.py‘>}

（4）sys.exc_info()方法

　　功能：返回值为一个包含异常类型、异常实例和异常回溯信息的元组

　　脚本：test.py

import sys

a = "abc"

try:
    int(a)
except:
    exc_type, exc_value, exc_traceback = sys.exc_info()
    print(exc_type)
    print(exc_value)
    print(exc_traceback)
    

>>python test.py
<class ‘ValueError‘>
invalid literal for int() with base 10: ‘abc‘
<traceback object at 0x7feb61a92dc8>

（5）sys.last_type

　　功能：返回最近一次捕获的异常的类型，只在交互式环境下可用

（6）sys.last_value

　　功能：返回最近一次捕获的异常的值，只在交互式环境下可用

（7）sys.last_traceback

　　功能：返回最近一次捕获的异常的追踪信息，只在交互式环境下可用