Bash – Environment variable not available in python

bashenvironment-variablespython

I have a pretty interesting problem regarding environment variables, and googling around didn't show me any meaningful results:

$ echo $BUCKET && python -c "import os; print os.environ['BUCKET']"
mule-uploader-demo
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/UserDict.py", line 23, in __getitem__
    raise KeyError(key)
KeyError: 'BUCKET'

So I have an environment variable that is available in bash but not inside python. How can this happen and how do I fix it? Here are some additional details:

  • The environment variable is set through a source envvars.sh command
  • The envvars.sh file contains only lines that look like this: KEY=value
  • I've reproduced this in both bash and zsh
  • If I do an export BUCKET=$BUCKET, it works

Best Answer

This has to do with the variable scope in bash. export makes your variable available to subprocesses, see for example:

→ export BUCKET=foo 
→ env | grep BUCKET
80:BUCKET=foo
→ PAIL=bar  
→ env | grep PAIL  # no output
→ python -c "import os; print os.environ['BUCKET']"
foo
→ python -c "import os; print os.environ['PAIL']"  
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "...", line 23, in __getitem__
    raise KeyError(key)
KeyError: 'PAIL'
→ CAN=baz python -c "import os; print os.environ['CAN']"
baz

so in a child process PAIL is a fail.

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