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Proper shebang for Python script

I'm usually using the following shebang declaration in my Python scripts:

#!/usr/bin/python

Recently, I've came across this shebang declaration:

#!/usr/bin/env python

In the script documentation, it was noted that using this form is "more portable".

What does this declaration mean? How come there's a space in the middle of the path? Does it actually contribute to protability?


j
jh314
#!/usr/bin/env python

is more portable because in general the program /usr/bin/env can be used to "activate" the desired command without full path.

Otherwise, you would have to specify the full path of the Python interpreter, which can vary.

So no matter if the Python interpreter was in /usr/bin/python or in /usr/local/bin/python or in your home directory, using #!/usr/bin/env python will work.


Great, thanks. Do you know does env work? does it run a full filesystem search, or relies on some path file?
@AdamMatan env uses the PATH variable in the environment by looking at each directory in it for a binary of the given name (python, in this case). If it finds it, it executes the program. This decouples the finding of the program from the execution, and since env is available on many systems in the standard location of /usr/bin, it is more portable. Better standardization leads to better portability.
If your script is Python 3 only and your target system might have a Python 2 executable in PATH then I recommend #!/usr/bin/env python3 instead.