[Python] How to set environment variables? [closed]

I am somehow a beginner with python.

so, i have this problem i set environment variables but they don't seem to work when i make a request. i used the set keyword to set the environment varibles. Also, another problem is that i can't use the env to display the existing environment variables.

this is how i am retrieving the variables,

APP_ID = os.environ.get('APP_ID')
API_KEY = os.environ.get('API_KEY')
USERNAME = os.environ.get('USERNAME')
PASSWORD = os.environ.get('PASSWORD')


and this is the Error i get.

File "d:\Programs\Projects\Workout-Tracker\main.py", line 24, in <module>
response = requests.post(url=nutrition_endpoint, json=params, headers=nutrition_headers)
File "c:\Users\yunus\.virtualenvs\storeFront-f1DWhIpC\Lib\site-packages\requests\api.py", line 115, in post
return request("post", url, data=data, json=json, **kwargs)
File "c:\Users\yunus\.virtualenvs\storeFront-f1DWhIpC\Lib\site-packages\requests\api.py", line 59, in request
return session.request(method=method, url=url, **kwargs)
~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "c:\Users\yunus\.virtualenvs\storeFront-f1DWhIpC\Lib\site-packages\requests\sessions.py", line 575, in request
prep = self.prepare_request(req)
File "c:\Users\yunus\.virtualenvs\storeFront-f1DWhIpC\Lib\site-packages\requests\sessions.py", line 484, in prepare_request

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