Why do people write #!/usr/bin/env python on the first line of a Python script?

Question

It seems to me like the files run the same without that line.

Answer 1

The main reason to do this is to make the script portable across operating system environments.

For example under mingw, python scripts use :

#!/c/python3k/python 

and under GNU/Linux distribution it is either:

#!/usr/local/bin/python 

or

#!/usr/bin/python

and under the best commercial Unix sw/hw system of all (OS/X), it is:

#!/Applications/MacPython 2.5/python

or on FreeBSD:

#!/usr/local/bin/python

However all these differences can make the script portable across all by using:

#!/usr/bin/env python