How to switch Python versions in Terminal?

Question

My Mac came with Python 2.7 installed by default, but I'd like to use Python 3.6.1 instead.

How can I change the Python version used in Terminal (on Mac OS)?

Please explain clearly and offer no third party version manager suggestions.

Solution 1

The simplest way would be to add an alias to python3 to always point to the native python installed. Add this line to the .bash_profile file in your $HOME directory at the last,

alias python="python3"

Doing so makes the changes to be reflected on every interactive shell opened.

Solution 2

As Inian suggested, you should alias python to point to python 3. It is very easy to do, and very easy to switchback, personally i have an alias setup for p2=python2 and p3=python3 as well to save on keystrokes. Read here for more information: How do I create a Bash alias?

Here is an example of doing so for python:

alias python=python3

Like so:

$ python --version
Python 2.7.6
$ python3 --version
Python 3.4.3
$ alias python=python3
$ python --version
Python 3.4.3

See here for the original: https://askubuntu.com/questions/320996/how-to-make-python-program-command-execute-python-3

Solution 3

You can just specify the python version when running a program:

for python 2:

python filename.py

for python 3:

python3 filename.py

Solution 4

pyenv is a 3rd party version manager which is super commonly used (18k stars, 1.6k forks) and exactly what I looked for when I came to this question.

Install pyenv.

Usage

$ pyenv install --list
Available versions:
  2.1.3
  [...]
  3.8.1
  3.9-dev
  activepython-2.7.14
  activepython-3.5.4
  activepython-3.6.0
  anaconda-1.4.0
  [... a lot more; including anaconda, miniconda, activepython, ironpython, pypy, stackless, ....]

$ pyenv install 3.8.1
Downloading Python-3.8.1.tar.xz...
-> https://www.python.org/ftp/python/3.8.1/Python-3.8.1.tar.xz
Installing Python-3.8.1...
Installed Python-3.8.1 to /home/moose/.pyenv/versions/3.8.1

$ pyenv versions
* system (set by /home/moose/.pyenv/version)
  2.7.16
  3.5.7
  3.6.9
  3.7.4
  3.8-dev

$ python --version
Python 2.7.17
$ pip --version
pip 19.3.1 from /home/moose/.local/lib/python3.6/site-packages/pip (python 3.6)

$ mkdir pyenv-experiment && echo "3.8.1" > "pyenv-experiment/.python-version"
$ cd pyenv-experiment

$ python --version
Python 3.8.1
$ pip --version
pip 19.2.3 from /home/moose/.pyenv/versions/3.8.1/lib/python3.8/site-packages/pip (python 3.8)

Solution 5

If you have python various versions of python installed,you can launch any of them using pythonx.x.x where x.x.x represents your versions.

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