passing variables to os.chdir in python -

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I have a very disappointing experience trying to change the directory in Python using the variable in the program. Specifically, suppose I have: 

  index = '999' os.environ ['dir_name'] = 'directory_name_' + index os.chdir ('$ dir_name') < / Code>

The OSERR returns: [Aron 2] There is no such file or directory: '$ dir_name'

and yet 

  Os.system ('echo $ dir_name')

Returns' Directory_Name_999 '(a valid directory name) and so on 

  os.chdir (' Directory_Name_999 ')

Replaces the directory without error and what can Python do os.syst Em understands that $ dir_name is a named dir_name . It checks its environment variable and finds it.

Python does not know what is "$ dir_name" , and it assumes that you are using a literal string, it tries to change that directory , And fails because there is no literal directory "$ dir_name" .

Instead, do: 

  Index = '999' os.environment ['dir_name'] = "directory_name_" + index os.chdir (os.environ [ 'Dir_name'])

You have the Ossystem ('cd $ dir_name') means: 

  Code>

But why mess with system call? Just do it python.


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