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I'm using os.getenv() to return a password to a python script. The password contains a capital I and when I save this as an environment variable it is saved correctly (after saving if I go to edit it and copy and paste it into notepad it shows correctly). The python os.getenv() method however returns the capital I as a lowercase l. Has anyone else encountered this and/or is there any other method I can use to return an env variable?

No, there is no alternative, and this can't be Python's fault.

On Windows, the os.environ mapping is initialised from the _wenviron global when Python starts. (Environment variables are given to a process when it starts running, if you changed the environment variables later on then you need to restart your process). The structure Windows gives Python is UTF-16, with keys always uppercase, values opaque Unicode text.

Python decodes the data from UTF-16 to Python str objects (unicode in Python 2), and creates a the os.environ mapping from that. That mapping then just maintains the uppercase nature of the keys, nothing else is changed. os.getenv is a helper function that uses os.environ.get(). There is no other API available or needed.

If you see unexpected data, you either made a mistake with how you set the variable, or you have changed the variable after Python already started. It's easy enough to mix I (capital India) and l (lowercase Lima); it is best just to avoid confusable characters like those and 0 (number zero), O (uppercase Oscar), 1 (number one) altogether.