How to switch between python 2 7 to python 3 from command line

Question

I m trying to find the best way to switch between the two python compilers  2 7 to 3 3  I ran the python script from the cmd like this      python ex1 py   Where do I set the  python  environment in the window s environment variable to point to either python 3 3 or 2 7   I am wondering if there is an easy way to switch between the two versions from the cmd line

User · Answer

No need for  quot tricks quot    Python 3 3 comes with PyLauncher  quot py exe quot   installs it in the path  and registers it as the  quot  py quot  extension handler   With it  a special comment at the top of a script tells the launcher which version of Python to run    python2 print  quot hello quot   Or   python3 print  quot hello quot    From the command line  py -3 hello py  Or py -2 hello py  py hello py by itself will choose the latest Python installed  or consult the PY PYTHON environment variable  e g  set PY PYTHON 3 6  See Python Launcher for Windows

User · Answer

In case you have both python 2 and 3 in your path  you can move up the Python27 folder in your path  so it search and executes python 2 first

User · Answer

They are 3 ways you can achieve this using the py command  py-launcher  in python 3  virtual environment or configuring your default python system path  For illustration purpose  you may see tutorial https   www youtube com watch v ynDlb0n27cw amp t 38s

User · Answer

There is an easier way than all of the above  You can use the PY PYTHON environment variable   From inside the cmd exe shell   For the latest version of Python 2  set PY PYTHON 2   For the latest version of Python 3  set PY PYTHON 3   If you want it to be permanent  set it in the control panel  Or use setx instead of set in the cmd exe shell

User · Answer

You can try to rename the python executable in the python3 folder to python3  that is if it was named python formally    it worked for me

User · Answer

For Windows 7  I just rename the python exe from the Python 3 folder to python3 exe and add the path into the environment variables  Using that  I can execute python test script py and the script runs with Python 2 7 and when I do python3 test script py  it runs the script in Python 3   To add Python 3 to the environment variables  follow these steps -    Right Click on My Computer and go to Properties  Go to Advanced System Settings  Click on Environment Variables and edit PATH and add the path to your Python 3 installation directory    For example

[python] How to switch between python 2.7 to python 3 from command line?

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