如何在python中读取Windows环境变量值? [英] How to read windows environment variable value in python?

问题描述

我尝试过:

os.environ['MyVar']

但是它没有用！ 有什么方法适合所有操作系统吗?

But it did not work! Is there any way suitable for all operating systems?

推荐答案

尝试使用以下内容:

os.getenv('MyVar')

从文档:

os.getenv(varname [，value])

os.getenv(varname[, value])

返回环境变量varname的值(如果存在)，否则返回value.值默认为无.

Return the value of the environment variable varname if it exists, or value if it doesn’t. value defaults to None.

可用性:Unix，Windows的大多数版本

Availability: most flavors of Unix, Windows

所以在测试之后:

>>> import os
>>> os.environ['MyVar'] = 'Hello World!'       # set the environment variable 'MyVar' to contain 'Hello World!'
>>> print os.getenv('MyVar')
Hello World!
>>> print os.getenv('not_existing_variable')
None
>>> print os.getenv('not_existing_variable', 'that variable does not exist')
that variable does not exist
>>> print os.environ['MyVar']
Hello World!
>>> print os.environ['not_existing_variable']
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.4/UserDict.py", line 17, in __getitem__
    def __getitem__(self, key): return self.data[key]
KeyError: 'not_existing_variable    

如果环境变量存在，您的方法也将起作用.使用os.getenv的区别在于，它返回None(或给定值)，而os.environ['MyValue']在变量不存在时给出KeyError异常.

Your method would work too if the environmental variable exists. The difference with using os.getenv is that it returns None (or the given value), while os.environ['MyValue'] gives a KeyError exception when the variable does not exist.

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