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mrgloom
Asked: 2019-07-13 09:47:36 +0800 CST

What do I do when "which python" doesn't show a location for python?

  • 772

which python shows nothing. The following command fixes the issue

/usr/bin$ sudo ln -s python3 python

But is it a common, safe solution?

which python
/usr/bin/python
command-line python

1 Answers

  1. Best Answer

    No, that's not safe or common at all.

    • Historically python refers to python2, not python3
    • Many python(2) scripts will break if run using the py3 interpreter
    • The reverse is also true: Many py3 scripts will break if run using the py2 interpreter.
    • There is no graceful failure - a script run using the wrong interpreter simply spits out a series of cryptic error and quits.

    See PEP 394 for all the details on what the 'python' command should symlink to. Don't stop at the 8-year-old first paragraph, read the entire history section to see how the recommendations have changed over time.

    Older releases of Ubuntu (16.04 and older) include both Python2 and Python3 with the default install. Changing python on these releases may break your system quite terribly.

    Newer releases of Ubuntu (18.04 and newer) include only Python3 with the default install. However, Python2 is trivial to install (sudo apt install python2).

    Python2 will reach End of Life during 2020, according to PEP 373. However, changing python afterward is still not recommended at present.

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