I'm using vscode on macOS and using nix to manage my environment. I do have python3.9 installed via homebrew as my system-default python, but I'm working on a project using a nix environment that is setting my path such that the only python executable available is python 3.8.
$ which python
/nix/store/mr2p1ycgj3wfppbw8ry2wwxg9r0xjz0z-python3-3.8.8-env/bin/python
$ whence python
/nix/store/mr2p1ycgj3wfppbw8ry2wwxg9r0xjz0z-python3-3.8.8-env/bin/python
$ whence python3
/nix/store/mr2p1ycgj3wfppbw8ry2wwxg9r0xjz0z-python3-3.8.8-env/bin/python
$ code .
The VSCode instance that comes up finds my 3.9 install as the default interpreter...
This causes a problem because the interpreter that's put on the path by nix is also the one with all my packages installed for this particular project, including developer utilities like black, flake8, pylint, etc... and my default 3.9 install does not necessarily have those.
It seems like there's a mechanism by which the Python extension discovers various python installs (I see in the extension output things where it tries to source virtualenvs and query pyenv), so what I think is happening is that it's finding a bunch of different python interpreters and blindly defaulting to the newest.
Is there any way to override the way the Python extension discovers python installs? I just want it to use the python interpreter that it finds on the path by default. I know I can override the interpreter per-project via the .vscode/settings.json, but that's a bit tedious to do for every project, and the way nix works that path may change occasionally. I already have "python.pythonPath": "python" in my vscode settings (which is the default anyway) - I was hoping that would work... it does not.
When we use "code." to open VS Code from the system terminal outside VS Code, it uses the latest version (highest version) of python installed in the system by default.
For directly opening an existing folder (containing python files) from VS Code, it defaults to using the python environment used last time, and for a new project that has not been selected, it also defaults to using the latest version (highest version) of python installed in the system .
You could click on the python environment in the lower left corner of VS Code, and then switch to the desired python environment in the options. In addition, it is recommended that you open the previously used project from VS Code (click File, Open Folder) and use the virtual environment in VS Code.
I'm teaching a beginners python class, the environment is Anaconda, VS Code and git (plus a few extras from a requirements.txt).
For the windows students this runs perfectly, however the mac students have an existing python (2.7) to contend with.
The windows students (i.e. they have a windows computer), their environment when they debug matches their console environment. However the mac students seem to be locked to their 2.7 environment.
I've tried aliasing, as suggested here and here
alias python2='python'
alias python='python3'
alias pip2='pip'
alias pip='pip3'
I've modified the .bash_profile file
echo 'export PATH="/Users/$USER/anaconda3/bin:$PATH"' >>.bash_profile
Both of these seem to work perfectly to modify their Terminal environments, when launched externally to VS Code. Neither seem to do anything to the environment launched from [cmd]+[`].
I've also tried conda activate base in the terminal, which seems to have no effect on a python --version or a which python
They can run things using python 3, but that means that they need to remember that they are different to the other 2/3 of the students. It's othering for them, and more work for me!
The students are doing fine, launching things from their external terminal, but it would streamline things greatly if the environments could be as consistent as possible across the OSs.
Whilst they are complete beginners, they can run a shell script. They currently have one that installs pip requirements and vs code extensions.
Is there a configuration that will keep the terminal in line with the debug env?
In my opinion the best practice is to create Python virtual environments (personally I love using conda environments, especially on Mac where you stuck with unremovable old Python version). Then VSCode will automatically (after installing very powerful Python extension) find all your virtual environments. This way you will teach your students a good practice of handling Python zoo a.k.a. package incompatibilities. Terminal environments settings will be consistent with VSCode, without being dependent on unneeded any more aliases. Obviously, virtual environments are OS independent, so you will be more consistent and remove unnecessary confusion between different students.
The additional bonus of the virtenvs is that you can create one exactly according to your requirements.txt and switch from one to another with a single click (in terminal it takes two commands: deactivate -> activate).
You can read more about how to handle Python virtual environments on VSCode site
Given the aliases are run just once and are not persistent in .bash_profile, python targets the default interpreter rather than the expected conda python3 interpreter.
Try to symlink conda's python3 executable to capture the python namespace
ln -sf /Users/$USER/anaconda3/bin/python3 /Users/$USER/anaconda3/bin/python
This will create or update the symlink. Use the same approach for pip and pip3.
Python in vscode let's you select which interpreter will be used to run the scripts.
It is in settings under "python.pythonPath", just set it to point to the interpreter of choice.
It can be set on a project basis as well (which is how you ensure that a project that has a virtual environment will execute using that interpreter and packages), you just select Workspace in the settings pane and add the desired python interpreter there.
So, I've been toying around with python environments and I think i screwed mine up.
So when I ran python in shell, it would tell me i'm running on 2.7
I'm on windows 10, and i need a python switcher for my next project so i download pywin and used pywin to switch it to 3.5
the command i used was
pywin setdefault 3.5
now when i type python it says
python is not recognized as an internal or external command.
but py produces
Python 2.7.12
Now i can't use pip, easy_install, virtualenv
all of these commands i used to use, i suddenly no longer have access to them.
I tried switching back
but it wont even recognize pywin anymore.
The best way to check which Python version is executed is to check your environment variables. Another way of checking this is using the which command. (open cmd and run which python).
But, first you need to start a new cmd prompt to ensure your environment variables are not altered.
On Windows, but also any OS, you need to check the PATH and PYTHONPATH variables.
For Windows, follow the recommandations available in the Python documentation.
If you're not very experienced with working with windows, installations, and other similar things, I would recommend that you uninstall python, delete all versions/folders containing python (compiled) files (those that were installed with python, not the ones you've written) and then reinstall python. The installer should re-set the path variable to the correct location.
Just reformatted my Mac to Yosemite and installed Python 2 & 3 using Homebrew. I've also setup some aliases in my bash_profile file which allows me to activate which version of Python I want to use. So if I type p3, it'll launch the python3 shell.
I'm wondering if it's possible to activate a specific version of Python without it starting the Python shell? So if I bring any files into the Terminal for instance, it'll use the version which I've activated?
Cheers!
Apologies if this has been answered elsewhere, I had a good search but I couldn't find anything.
Rather than writing your own scripts to manage different Python versions, I would suggest using a highly-used manager that has been tested in and out by the community: pyenv. With pyenv you can:
Easily install several different Python versions from the command line with no issues of them fighting (pyenv install 3.4.2)
Create virtual environments from any one of those versions if you want to compartmentalize the packages that are available (pyenv virtualenv 3.4.2 mypy3projectvenv), and
Set specific environments or versions to be active either
globally (pyenv global [version-or-venv]),
locally in and below folders you configure (pyenv local [ver-or-venv]), usually useful for projects that you have at a specific version/virtualenv, and
local to the shell until closed (pyenv shell [ver-or-venv]) (this is perhaps most-similar to your putative p3 command.
After setting the Python you want to use, all Python-related calls are redirected to their appropriate target (e.g. python, pip, easy_install, ipython*, django-admin*). Don't execute the Python scripts with any special command, just call them normally (or prefix a standard #!/usr/bin/env python shebang)
*If installed in that version/virtualenv
If you use the pyenv-installer script:
curl -L https://raw.githubusercontent.com/yyuu/pyenv-installer/master/bin/pyenv-installer | bash
Then add the couple lines it tells you to your ~/.bash_profile script (and either source it or restart bash)...you'll be up and running in seconds. The trick is usually installing all the Python build dependencies with brew (sqlite, OpenSSH, zlib...), but after that then you're golden.
I do most of my programming in Python 3.x on Windows 7, but now I need to use the Python Imaging Library (PIL), ImageMagick, and wxPython, all of which require Python 2.x.
Can I have both Python 2.x and Python 3.x installed in Windows 7? When I run a script, how would I "choose" which version of Python should run it? Will the aforementioned programs be able to handle multiple versions of Python installed at once? I have searched for hours and hours for how to do this to no avail.
Thanks.
I found that the formal way to do this is as follows:
Just install two (or more, using their installers) versions of Python on Windows 7 (for me work with 3.3 and 2.7).
Follow the instuctions below, changing the parameters for your needs.
Create the following environment variable (to default on double click):
Name: PY_PYTHON
Value: 3
To launch a script in a particular interpreter, add the following shebang (beginning of script):
#! python2
To execute a script using a specific interpreter, use the following prompt command:
> py -2 MyScript.py
To launch a specific interpreter:
> py -2
To launch the default interpreter (defined by the PY_PYTHON variable):
> py
Resources
Documentation: Using Python on Windows
PEP 397 - Python launcher for Windows
What I did was download both 2.7.6 and 3.3.4. Python 3.3.4 has the option to add the path to it in the environment variable so that was done. So basically I just manually added Python 2.7.6.
How to...
Start > in the search type in environment select "Edit environment variables to your account"1
Scroll down to Path, select path, click edit.
Add C:\Python27;
so you should have paths to both versions of Python there, but if you don't this you can easily edit it so that you do..... C:\Python27;C:\Python33;
Navigate to the Python27 folder in C:\ and rename a copy of python.exe to python2.exe
Navigate to the Python34 folder in C:\ and rename a copy of python.exe to python3.exe
Test: open up commmand prompt and type python2 ....BOOM! Python 2.7.6. exit out.
Test: open up commmand prompt and type python3 ....BOOM! Python 3.4.3. exit out.
Note: (so as not to break pip commands in step 4 and 5, keep copy of python.exe in the same directory as the renamed file)
I have multiple versions in windows.
I just change the exe name of the version I'm not defaulting to.
python.exe --> python26.exe
pythonw.exe --> pythonw26.exe
As for package installers, most exe installers allow you to choose the python install to add the package too.
For manual installation check out the --prefix option to define where the package should be installed:
http://docs.python.org/install/index.html#alternate-installation-windows-the-prefix-scheme
If you use Anaconda Python, you can easily install various environments.
Say you had Anaconda Python 2.7 installed and you wanted a python 3.4 environment:
conda create -n py34 python=3.4 anaconda
Then to activate the environment:
activate py34
And to deactive:
deactivate py34
(With Linux, you should use source activate py34.)
Links:
Download Anaconda Python
Instructions for environments
To install and run any version of Python in the same system follow my guide below.
For example say you want to install Python 2.x and Python 3.x on the same Windows system.
Install both of their binary releases anywhere you want.
When prompted do not register their file extensions and
do not add them automatically to the PATH environment variable
Running simply the command python the executable that is first met in PATH will be chosen for launch. In other words, add the Python directories manually. The one you add first will be selected when you type python. Consecutive python programs (increasing order that their directories are placed in PATH) will be chosen like so:
py -2 for the second python
py -3 for the third python etc..
No matter the order of "pythons" you can:
run Python 2.x scripts using the command: py -2 (Python 3.x functionality) (ie. the first Python 2.x installation program found in your PATH will be selected)
run Python 3.x scripts using the command: or py -3 (ie. the first Python 3.x installation program found in your PATH will be selected)
In my example I have Python 2.7.14 installed first and Python 3.5.3. This is how my PATH variable starts with:
PATH=C:\Program Files\Microsoft MPI\Bin\;C:\Python27;C:\Program Files\Python_3.6\Scripts\;C:\Program Files\Python_3.6\;C:\ProgramData\Oracle\Java\javapath;C:\Program Files (x86)\Common Files\Intel\Shared
...
Note that Python 2.7 is first and Python 3.5 second.
So running python command will launch python 2.7 (if Python 3.5 the same command would launch Python 3.5).
Running py -2 launches Python 2.7 (because it happens that the second Python is Python 3.5 which is incompatible with py -2).
Running py -3 launches Python 3.5 (because it's Python 3.x)
If you had another python later in your path you would launch like so: py -4. This may change if/when Python version 4 is released.
Now py -4 or py -5 etc. on my system outputs: Requested Python version (4) not installed or Requested Python version (5) not installed etc.
Hopefully this is clear enough.
Here's what you can do:
Install cmder.
Open and use Cmder as you would with you cmd terminal.
Use the command alias to create command aliases.
I did the following:
alias python2 = c:\python27\python.exe
alias python3 = c:\python34\python.exe
And that's it! ;-)
I actually just thought of an interesting solution. While Windows will not allow you to easily alias programs, you can instead create renamed batch files that will call the current program.
Instead of renaming the executable which will break a lot of thing including pip, create the file python2.bat in the same directory as the python2.exe. Then add the following line:
%~dp0python %*
What does this archaic syntax mean? Well, it's a batch script, (Windows version of bash). %~dp0 gets the current directory and %* will just pass all the arguments to python that were passed to the script.
Repeat for python3.bat
You can also do the same for pip and other utilities, just replace the word python in the file with pip or whathever the filename. The alias will be whatever the file is named.
Best of all, when added to the PATH, Windows ignores the extension so running
python3
Will launch the python3 version and and the command python2 will launch the python2 version.
BTW, this is the same technique Spyder uses to add itself to the path on Windows. :)
Starting version 3.3 Windows version has Python launcher, please take a look at section 3.4. Python Launcher for Windows
You can install multiple versions of Python one machine, and during setup, you can choose to have one of them associate itself with Python file extensions. If you install modules, there will be different setup packages for different versions, or you can choose which version you want to target. Since they generally install themselves into the site-packages directory of the interpreter version, there shouldn't be any conflicts (but I haven't tested this). To choose which version of python, you would have to manually specify the path to the interpreter if it is not the default one. As far as I know, they would share the same PATH and PYTHONPATH variables, which may be a problem.
Note: I run Windows XP. I have no idea if any of this changes for other versions, but I don't see any reason that it would.
What I have done on my own windows computer where I have Python 2.7 and Python 3.4 installed is I wrote a simple .bat file in the same directory as my Python.exe files. They look something like,
cmd /k "c:\python27\python.exe" %*
The %* allows you to add arguments (Python files) afterwards. I believe /k keeps the prompt open after it finishes running the script. Then I save that as python27.bat Then I go to my Python 3 directory and make a bat file there. Now in my command line I can write
Python27 helloworld.py
Or
Python34 helloworld.py
And they will run in their respective versions of Python. Make sure that c:\python27 and c:\python34 are in your environment variables.
I got my answer from here
I did this in three steps by following the instructions here: This is all taken directly from here: http://ipython.readthedocs.io/en/stable/install/kernel_install.html. I'm currently running Python 2.x on Windows 8 and have Anaconda 4.2.13 installed.
1) First install the latest version of python:
conda create -n python3 python=3 ipykernel
2) Next activate python3
activate python3
3) Install the kernel:
python -m ipykernel install --user
If you have Python 3 installed and want to install 2, switch the 2 and the 3 above. When you open a new notebook, you can now choose between Python 2 or 3.
Check your system environment variables after installing Python, python 3's directories should be first in your PATH variable, then python 2.
Whichever path variable matches first is the one Windows uses.
As always py -2 will launch python2 in this scenario.
I have encountered that problem myself and I made my launchers in a .bat so you could choose the version you want to launch.
The only problem is your .py must be in the python folder, but anyway here is the code:
For Python2
#echo off
title Python2 Launcher by KinDa
cls
echo Type the exact version of Python you use (eg. 23, 24, 25, 26)
set/p version=
cls
echo Type the file you want to launch without .py (eg. hello world, calculator)
set/p launch=
path = %PATH%;C:\Python%version%
cd C:\Python%version%
python %launch%.py
pause
For Python3
#echo off
title Python3 Launcher by KinDa
cls
echo Type the exact version of Python you use (eg. 31, 32, 33, 34)
set/p version=
cls
echo Type the file you want to launch without .py (eg. hello world, calculator)
set/p launch=
cls
set path = %PATH%:C:\Python%version%
cd C:\Python%version%
python %launch%.py
pause
Save them as .bat and follow the instructions inside.
Install the one you use most (3.3 in my case) over the top of the other. That'll force IDLE to use the one you want.
Alternatively (from the python3.3 README):
Installing multiple versions
On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (--prefix argument to the configure script)
you must take care that your primary python executable is not overwritten by the
installation of a different version. All files and directories installed using
"make altinstall" contain the major and minor version and can thus live
side-by-side. "make install" also creates ${prefix}/bin/python3 which refers to
${prefix}/bin/pythonX.Y. If you intend to install multiple versions using the
same prefix you must decide which version (if any) is your "primary" version.
Install that version using "make install". Install all other versions using
"make altinstall".
For example, if you want to install Python 2.6, 2.7 and 3.3 with 2.7 being the
primary version, you would execute "make install" in your 2.7 build directory
and "make altinstall" in the others.
I just had to install them. Then I used the free (and portable) soft at http://defaultprogramseditor.com/ under "File type settings"/"Context menu"/search:"py", chose .py file and added an 'open' command for the 2 IDLE by copying the existant command named 'open with IDLE, changing names to IDLE 3.4.1/2.7.8, and remplacing the files numbers of their respective versions in the program path. Now I have just to right click the .py file and chose which IDLE I want to use. Can do the same with direct interpreters if you prefer.
I use a simple solution to switch from a version to another version of python, you can install all version you want. All you have to do is creating some variable environment.
In my case, I have installed python 2.7 and python 3.8.1, so I have created this environment variables:
PYTHON_HOME_2.7=<path_python_2.7>
PYTHON_HOME_3.8.1=<path_python_3.8.1>
PYTHON_HOME=%PYTHON_HOME_2.7%
then in my PATH environment variable I put only %PYTHON_HOME% and %PYTHON_HOME%\Scripts. In the example above I'm using the version 2.7, when I want to switch to the other version I have only to set the PYTHON_HOME=%PYTHON_HOME_3.8.1%.
I use this method to switch quickly from a version to another also for JAVA, MAVEN, GRADLE,ANT, and so on.
Only Works if your running your code in your Python IDE
I have both Python 2.7 and Python 3.3 installed on my windows operating system. If I try to launch a file, it will usually open up on the python 2.7 IDE. How I solved this issue, was when I choose to run my code on python 3.3, I open up python 3.3 IDLE(Python GUI), select file, open my file with the IDLE and save it. Then when I run my code, it runs to the IDLE that I currently opened it with. It works vice versa with 2.7.
I have installed both python 2.7.13 and python 3.6.1 on windows 10pro and I was getting the same "Fatal error" when I tried pip2 or pip3.
What I did to correct this was to go to the location of python.exe for python 2 and python 3 files and create a copy of each, I then renamed each copy to python2.exe and python3.exe depending on the python version in the installation folder. I therefore had in each python installation folder both a python.exe file and a python2.exe or python3.exe depending on the python version.
This resolved my problem when I typed either pip2 or pip3.
If you can't get anything else to work, open an interpreter in whichever version you choose (I prefer using iPython) and:
import subprocess
subprocess.call('python script.py -flags')
This uses whichever python version you are currently operating under. Works fine for a single script, but will quickly get out of hand if there are lots of scripts you run, in which case you can always make a batch file with all of these calls inside. Not the most elegant answer, but it works.
Is there a way to make aliases for different python version a la Linux?