How can I configure windows command dialog to run different python versions in it? For example when I type python2 it runs python 2.7 and when I type python3 it runs python 3.3? I know how to configure environment variables for one version but two? I mean something like Linux terminal.
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3 Answers
I also met the case to use both python2 and python3 on my Windows machine. Here's how i resolved it:
- download python2x and python3x, installed them.
- add
C:\Python35;C:\Python35\Scripts;C:\Python27;C:\Python27\Scriptsto environment variablePATH. - Go to
C:\Python35to renamepython.exetopython3.exe, also toC:\Python27, renamepython.exetopython2.exe. - restart your command window.
- type
python2 scriptname.py, orpython3 scriptname.pyin command line to switch the version you like.
2 Comments
martineau
To which environment variable did you add all the Python paths? As for renaming the
python.exe files, how does doing that affect things when doing minor upgrades, say from version 2.7.x to 2.7.x+y, which normally would both be located in the same C:\Python27 directory?
alansiqueira27
what if I want to execute something like "pytest file.py"? It does not work like "python2 pytest file.py"
Python 3.3 introduces Python Launcher for Windows that is installed into c:\Windows\ as py.exe and pyw.exe by the installer. The installer also creates associations with .py and .pyw. Then add #!python3 or #!python2 as the first lline. No need to add anything to the PATH environment variable.
Update: Just install Python 3.3 from the official python.org/download. It will add also the launcher. Then add the first line to your script that has the .py extension. Then you can launch the script by simply typing the scriptname.py on the cmd line, od more explicitly by py scriptname.py, and also by double clicking on the scipt icon.
The py.exe looks for C:\PythonXX\python.exe where XX is related to the installed versions of Python at the computer. Say, you have Python 2.7.6 installed into C:\Python27, and Python 3.3.3 installed into C:\Python33. The first line in the script will be used by the Python launcher to choose one of the installed versions. The default (i.e. without telling the version explicitly) is to use the highest version of Python 2 that is available on the computer.
16 Comments
hamidfzm
Please explain more I couldn't understand what you have said!
pepr
You can always rename your
C:\Python33\python.exe to the C:\Python33\python3.exe. However, it is better to use explicitly py -3 scriptname.py. It is even better to put the information into the script, and then launch your scripts for either version the uniform way.pepr
@BlackJack: I see. Anyway, you can create a new copy named
python3.exe. However, using the Python Launcher for Windows is better, and there is no need for doing such things.pepr
@ConradB OK. But the question is how to run different Python version in
cmd. When using Python Launcher for Windows, the Python is not in the path at all -- nor the system, nor the user paths. That is because py.exe is in c:\Windows. And if you do not want to modify the script, you can always call py -3 myscript.py for Python 3 or py -2 myscript.py for Python 2. Default today for py myscript.py uses Python 3 interpreter.
johan d
To quote myself, " we can specify the minor " -> it is possible, and sometimes even necessary. As an example, my own config hosts a 3.6 and a 3.7 version, and I have a lib that is not (yet?) compatible with 3.7. I fixed my issues by specifying a compatible minor version.
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I would suggest using the Python Launcher for Windows utility that was introduced into Python 3.3. You can manually download and install it directly from the author's website for use with earlier versions of Python 2 and 3.
Regardless of how you obtain it, after installation it will have associated itself with all the standard Python file extensions (i.e. .py, .pyw, .pyc, and .pyo files). You'll not only be able to explicitly control which version is used at the command-prompt, but also on a script-by-script basis by adding Linux/Unix-y shebang #!/usr/bin/env pythonX comments at the beginning of your Python scripts.