Why doesn't "export" overwrite existing values?

Question

Why isn't export python=/usr/local/bin/python2.7 changing the path to python?

I am baffled by the following:

$ which python
/usr/bin/python
$ export python=/usr/local/bin/python2.7
$ which python
/usr/bin/python

I'm using OSX v10.12.

Answer 1

The program which determines the path of shell commands.

What you did in the second statement is set a variable named python.

Shell commands and variables are entirely different things.

What you'd might like to use is an alias.

alias python="/usr/local/bin/python2.7"

Note, that (except in zsh or tcsh, or if your which is itself a shell function that invokes GNU which, as recommended by its manual), which will not show the alias, while e.g. type python will.