(env_name, value)
Set the environment variable 'env_name' to 'value'

    Save previous value, yield, and then restore the previous value stored in
    the environment variable 'env_name'.

    If 'value' is None, do nothing
Set the environment variable 'env_name' to 'value'
Set the environment variable env_name to value
def set_environ(env_name, value):
    """Set the environment variable 'env_name' to 'value'

    Save previous value, yield, and then restore the previous value stored in
    the environment variable 'env_name'.

    If 'value' is None, do nothing"""
    value_changed = value is not None
    if value_changed:
        old_value = os.environ.get(env_name)
        os.environ[env_name] = value
    try:
        yield
    finally:
        if value_changed:
            if old_value is None:
                del os.environ[env_name]
            else:
                os.environ[env_name] = old_value
def set_environ ( env_name , value ) : value_changed = value is not None if value_changed : old_value = os . environ . get ( env_name ) os . environ [ env_name ] = value try : yield finally : if value_changed : if old_value is None : del os . environ [ env_name ] else : os . environ [ env_name ] = old_value