Python - temporarily modify the current process's environment

Question

I use the following code to temporarily modify environment variables.

@contextmanager
def _setenv(**mapping):
    \"\"\"``with`` context to temporarily modi         


        

Answer 1

I was looking to do the same thing but for unit testing, here is how I have done it using the unittest.mock.patch function:

def test_function_with_different_env_variable():
    with mock.patch.dict('os.environ', {'hello': 'world'}, clear=True):
        self.assertEqual(os.environ.get('hello'), 'world')
        self.assertEqual(len(os.environ), 1)

Basically using unittest.mock.patch.dict with clear=True, we are making os.environ as a dictionary containing solely {'hello': 'world'}.

• Removing the clear=True will let the original os.environ and add/replace the specified key/value pair inside {'hello': 'world'}.

• Removing {'hello': 'world'} will just create an empty dictionary, os.envrion will thus be empty within the with.