Install Python 3 Alongside Python 2 on Windows 10

I recently needed to test an application at work with Python 3. It’s a hard requirement that I keep the ability to run Python 2 code for my job, so I installed Python 3 alongside my existing Python 2 installation. Since it required more work than just running the installer and calling it done, I documented the process below.

This method does not require administrative privileges to install for your user account, (it will if you need to install for all users on a machine, however).

The first step is to get Python 3 installed.

1. Get latest installer executable from: https://www.python.org/getit/
2. Launch the installer, un-check the box for “Install for all users”, and click install.

After the installer completes, Python will be installed in, ‘C:\Users\[YOUR-USER]\AppData\Local\Programs\Python\Python3[VERSION]’, and will be automatically added to your PATH. Because Python 2’s directory is already in your PATH and has a program under the same name ‘python.exe’, it will always launch the old Python 2 executable. Let’s fix that.

1. Go into the Python 3 install directory (above) and copy python.exe to python3.exe
2. Open a new Powershell window and test with python3 --version .

Sweet! Python 3 is now installed alongside Python 2 and can easily called with python3.

Note: Pip3 will be automatically get installed with the alias ‘pip3’ so there is no need to worry about copying pip.exe.

Note #2: When calling Python 3 modules, it’s usually a good idea to use ‘python3 -m module_name’, instead of any shell shorthand name because if you have a module installed for Python 2, it will usually try to use that. Example, virtualenv. Running virtualenv folder, from cmd or Powershell will create a Python 2 virtual environment, whereas using python3 -m virtualenv folder, will always create a Python 3 virtual environment.

Hopefully that helped you. If you encounter any errors I didn’t account for, drop a response below and I’ll add it to this post.

Thanks!