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Virtualenv Wrapper is installing both python version in the virtual environments

The major issue is i only want python3.0+ version of python in my virtualenvironment. But when i create a virtualenvironment with mkvirtualenv then both python2 and python3 gets install inside my virtualenvironments.
Images:
Bashrc Settings :
virtualenv settings :

When you type pythonTab bash shows all pythons in the $PATH — some from /usr/bin/, some from $VIRTUAL_ENV/bin/. virtualenv doesn't separate bash from the system, it only protects one version of Python from the global site-packages/ directory.
If you've configured locate you can see all your pythons using command
locate bin/python
To limit the list for those in $PATH:
for p in ${PATH//:/ }; do
ls $p/python* 2>/dev/null
done

Python not running from command line but running from anaconda shell

I have installed python 2.7 on my computer. I am able to run python from anaconda but not from command line. The command line says python not found.
Also, how can I have two python versions(2.7 and 3.4) at the same time?

run this command line:
ipython myprogram.py
To create a new virtual environment with a specific version of python, using conda:
conda create -n my_env python=3.6
To switch environments:
on osx/linux: source activate my_env
on windows: activate my_env
to exit source deactivate, or deactivate on windows
more details here: managing conda environments

It can be, that two different python versions are running on your pc. Make sure, you have the same version running on anaconda and the command line.

If on windows just install them both and rename the python.exe tot python2.exe for version 2.7 and python3.exe for python 3.
Now you can call python 2 in the command prompt with
python2
and you can acces python3 with
python3
Also make sure your python path is in your environment variables.

Sure, you can have two Pythons installed.
The command line searches the executable you wanted to run (python, in this case) in the current directory and in all directories specified in PATH environment variable.
It depends on OS, but search how to insert the binary directory (where the python executable resides) into the PATH environment variable.

How to create virtual env with python3

I am using python 2.7 + virtualenv version 1.10.1 for running myproject projects. Due to some other projects requirement I have to work with other version of python(Python 3.5) and Django 1.9. For this I have installed python in my user directory. Also I have dowloaded and installed virtualenv( version - 15.1.0) into my user directory.
But whenever I am trying to create virtual env I am getting the below error
python virtualenv/virtualenv.py myproject
Using base prefix '/home/myuser/python3'
New python executable in /home/mount/myuser/project_python3/myproject/bin/python
ERROR: The executable /home/mount/myuser/project_python3/myproject/bin/python is not functioning
ERROR: It thinks sys.prefix is '/home/myuser/python3' (should be '/home/mount/myuser/project_python3/myproject')
ERROR: virtualenv is not compatible with this system or executable
Can anybody tell what I am doing wrong with this

In Python 3.6+, the pyvenv module is deprecated. Use the following one-liner instead:
python3 -m venv <myenvname>
This is the recommended way to create virtual environments by the Python community.

To create virtual env
virtualenv -p python3 venv_name
This will create new python executable in baseDirectory/bin/python3
How to activate newely created Venv:
cd baseDirectory/bin/
source activate
Deactivate new venv
deactivate
UPDATE_1
This method has been depreciated as The use of venv is now recommended for creating virtual environments.
Please check this link for updated answer

Python already ships with its builtin "virtualenv" called venv since version 3.3. You no longer need to install or download the virtualenv scripts for Python 3.3+.
https://docs.python.org/3/library/venv.html
Check that your installation provided the pyvenv command that should take care of creating the "virtualenv". Arguments are similar to the classic virtualenv project.
$ pyvenv --help
usage: venv [-h] [--system-site-packages] [--symlinks | --copies] [--clear]
[--upgrade] [--without-pip]
ENV_DIR [ENV_DIR ...]
Creates virtual Python environments in one or more target directories.
positional arguments:
ENV_DIR A directory to create the environment in.
optional arguments:
-h, --help show this help message and exit
--system-site-packages
Give the virtual environment access to the system
site-packages dir.
--symlinks Try to use symlinks rather than copies, when symlinks
are not the default for the platform.
--copies Try to use copies rather than symlinks, even when
symlinks are the default for the platform.
--clear Delete the contents of the environment directory if it
already exists, before environment creation.
--upgrade Upgrade the environment directory to use this version
of Python, assuming Python has been upgraded in-place.
--without-pip Skips installing or upgrading pip in the virtual
environment (pip is bootstrapped by default)
Once an environment has been created, you may wish to activate it, e.g. by
sourcing an activate script in its bin directory.

virtualenv is the tool of choice for Python 2, while venv handles the task in Python 3.
Yet you can create the virtual environment for Python 3 using any of them.
Using venv
python3 -m venv virtualenvname
Command Syntax:
/path/to/python3 -m venv /path/to/directory/virtual_env_name
Using virtualenv
virtualenv -p python3 virtualenvname
Command Syntax:
virtualenv -p /path/to/python3 /path/to/directory/virtual_env_name
Activate the virtual environment
On Linux, Unix or MacOS, using the terminal or bash shell:
source /path/to/venv/bin/activate
e.g. source virtualenvname/bin/activate
On Unix or MacOS, using the csh shell:
source /path/to/venv/bin/activate.csh
On Unix or MacOS, using the fish shell:
source /path/to/venv/bin/activate.fish
On Windows using the Command Prompt:
path\to\venv\Scripts\activate.bat
On Windows using PowerShell:
path\to\venv\Scripts\Activate.ps1
Deactivating the virtual environment
On Linux, Unix or MacOS, using the terminal or bash shell:
deactivate
On Windows using the Command Prompt:
path\to\venv\Scripts\deactivate.bat
On Windows using PowerShell:
deactivate
This answer is for those who may use a different OS.

Since the launch of Python version 3.3, there has been no need to download the virtualenv package separately as it comes built-in in Python.
Refer to the documentation to gain complete insights on it.
Test the installation of virtualenv:
$ virtualenv --version
Usage:
1.Creating a virtual environment:
$ virtualenv --system-site-packages -p python3 ./virtual_env_name
2.For enabling it, use the following command:
$ source ./virtual_env_name/bin/activate
3.For disabling the virtual environment and get back to working with the local environment:
$ deactivate
For listing down the packages in the virtual environment, use the
following command:
$ pip3 list

I install it using the command (for Python 3.x),
$ python3 -m venv env

To create a virtual environment in python3:
virtualenv -p /usr/bin/python3 virtualenvname
After creating the virtual environment, we need to activate it using the below command:
source virtualenvname/bin/activate
to deactivate use the below command:
deactivate

If you are on windows.
manually download and install the version of python you want from the official site
after installation, search "python" to locate the folder, so you can identify the path
get the path of the .exe (for example: C:\Users\Path\Programs\Python\Python38\python.exe)
Inside the folder of which you want to create the environment...start bash or VSCode terminal, or whatever command prompt, type [python .exe path] -m venv [env name] like this:
C:/Users/Path/Programs/Python/Python38/python.exe -m venv myenv
(Note that you have to change forward slash to backward slash for the path on step 4)
Activate the environment like so:
source myenv/Scripts/activate

Install virtualenvwrapper on top of virtualenv to simplify things.
Follow the blog to install in easy steps: virtualenvwrapper
Steps to create it:
mkvirtualenv -p /usr/bin/python3
Install packages using - pip install package_name
workon - activates the virtualenv, deactivate - deactivates the viirtualenv

Python2 and Python3 both in windows 10

I used Anaconda for python.
python2 is installed in
D:\Python\Anaconda2
python3 is installed in
D:\Python\Anaconda3
python3 is the default.
created two environmental variables with name: python2 and python2 and selected respective python.exe from different folder respectively.
my setup.py supports only python2.
when i run command from cmd python setup.py install it says it does not support.
If I rename D:\Python\Anaconda2\python.exe to D:\Python\Anaconda2\python2.exe and change the environment path file accordingly it works. But I dnt want to change the file name (as it may break other apps, like conda says unable to create process, etc).
Windows 10 Pro, 64 bit.
setup.py location:
E:\Program Files\IBM\ILOG\CPLEX_Studio1251\cplex\python\x64_win64
How to overcome this? Want python2 setup.py install for python2 compiler and python3 setup.py install for python3 compiler, without renaming.
How to install setup.py by running D:\Python\Anaconda2\python.exe?

I'm not sure whether this directly answers your question,but anaconda manages environments for you. Reference
You should be able to type into your Anaconda prompt to create your environment:
conda create --name pyenv python=2.7
and then list your environments:
conda info --envs
and lastly activate your environment python 2 or python 3 environments:
activate pyenv
These separate environments with their own versions of python are saved in the anaconda folder under the envs folder
/Anaconda3/envs/pyenv/python

Here is how you can use both python2 and python3 in windows 10
Install python2 from here https://www.python.org/downloads/
Install python3 from here https://www.python.org/downloads/
Enter windows keys and type "Edit the system environment variables"
Click on Path and enter Edit button.
Add path to both version of python. (Important) Here i have listed python3 and python2 in order because i want to see version 2 by python --version and version3 by python3 --version.
Go to C:\python310 in windows (or whatever the name is for python3) and update executable file to python3 instead of python.
Save and exit.
Now,
python --version // python 2
python3 --version // python 3
If you want it otherwise, update executable file of python2 to python2 instead of python. And update PATH variables to list python2 and python3 in order.

pip installs packages successfully, but executables not found from command line

I am working on mac OS X Yosemite, version 10.10.3.
I installed python2.7 and pip using macport as done in
http://johnlaudun.org/20150512-installing-and-setting-pip-with-macports/
I can successfully install packages and import them inside my python environment and python scripts. However any executable associated with a package that can be called from the command line in the terminal are not found.
Does anyone know what might be wrong? (More details below)
For example while installing a package called "rosdep" as instructed in http://wiki.ros.org/jade/Installation/Source
I can run: sudo pip install -U rosdep
which installs without errors and corresponding files are located in /opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
However if I try to run : sudo rosdep init,
it gives an error : "sudo: rosdep: command not found"
This is not a package specific error. I get this for any package installed using pip on my computer. I even tried adding
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
to my $PATH.
But the executables are not found on the command line, even though the packages work perfectly from within python.

I know the question asks about macOS, but here is a solution for Linux users who arrive here via Google.
I was having the issue described in this question, having installed the pdfx package via pip.
When I ran it however, nothing...
pip list | grep pdfx
pdfx (1.3.0)
Yet:
which pdfx
pdfx not found
The problem on Linux is that pip install ... drops scripts into ~/.local/bin and this is not on the default Debian/Ubuntu $PATH.
Here's a GitHub issue going into more detail: https://github.com/pypa/pip/issues/3813
To fix, just add ~/.local/bin to your $PATH, for example by adding the following line to your .bashrc file:
export PATH="$HOME/.local/bin:$PATH"
After that, restart your shell and things should work as expected.

Solution
Based on other answers, for linux and mac you can run the following:
echo "export PATH=\"`python3 -m site --user-base`/bin:\$PATH\"" >> ~/.bashrc
source ~/.bashrc
instead of python3 you can use any other link to python version: python, python2.7, python3.6, python3.9, etc.
instead of .bashrc, choose the rc file from your favourite shell.
Explanation
In order to know where the user packages are installed in the current OS (win, mac, linux), we run:
python3 -m site --user-base
We know that the scripts go to the bin/ folder where the packages are installed.
So we concatenate the paths:
echo `python3 -m site --user-base`/bin
Then we export that to an environment variable.
export PATH=\"`python3 -m site --user-base`/bin:\$PATH\"
Finally, in order to avoid repeating the export command we add it to our .bashrc file and we run source to run the new changes, giving us the suggested solution mentioned at the beginning.

On macOS with the default python installation you need to add /Users/<you>/Library/Python/2.7/bin/ to your $PATH.
Add this to your .bash_profile:
export PATH="/Users/<you>/Library/Python/2.7/bin:$PATH"
That's where pip installs the executables.
Tip: For non-default python version which python to find the location of your python installation and replace that portion in the path above. (Thanks for the hint Sanket_Diwale)

check your $PATH
tox has a command line mode:
audrey:tests jluc$ pip list | grep tox
tox (2.3.1)
where is it?
(edit: the 2.7 stuff doesn't matter much here, sub in any 3.x and pip's behaving pretty much the same way)
audrey:tests jluc$ which tox
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin/tox
and what's in my $PATH?
audrey:tests jluc$ echo $PATH
/opt/chefdk/bin:/opt/chefdk/embedded/bin:/opt/local/bin:..../opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin...
Notice the /opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin? That's what allows finding my pip-installed stuff
Now, to see where things are from Python, try doing this (substitute rosdep for tox).
$python
>>> import tox
>>> tox.__file__
that prints out:
'/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/tox/__init__.pyc'
Now, cd to the directory right above lib in the above. Do you see a bin directory? Do you see rosdep in that bin? If so try adding the bin to your $PATH.
audrey:2.7 jluc$ cd /opt/local/Library/Frameworks/Python.framework/Versions/2.7
audrey:2.7 jluc$ ls -1
output:
Headers
Python
Resources
bin
include
lib
man
share

If you're installing using --user (e.g. pip3.6 install --user tmuxp), it is possible to get the platform-specific user install directory from Python itself using the site module. For example, on macOS:
$ python2.7 -m site --user-base
/Users/alexp/Library/Python/2.7
By appending /bin to this, we now have the path where package executables will be installed. We can dynamically populate the PATH in your shell's rc file based on the output; I'm using bash, but with any luck this is portable:
# Add Python bin directories to path
python3.6 -m site &> /dev/null && PATH="$PATH:`python3.6 -m site --user-base`/bin"
python2.7 -m site &> /dev/null && PATH="$PATH:`python2.7 -m site --user-base`/bin"
I use the precise Python versions to reduce the chance of the executables just "disappearing" when Python upgrades a minor version, e.g. from 3.5 to 3.6. They'll disappear because, as can be seen above, the user installation path may include the Python version. So while python3 could point to 3.5 or 3.6, python3.6 will always point to 3.6. This needs to be kept in mind when installing further packages, e.g. use pip3.6 over pip3.
If you don't mind the idea of packages disappearing, you can use python2 and python3 instead:
# Add Python bin directories to path
# Note: When Python is upgraded, packages may need to be re-installed
# or Python versions managed.
python3 -m site &> /dev/null && PATH="$PATH:`python3 -m site --user-base`/bin"
python2 -m site &> /dev/null && PATH="$PATH:`python2 -m site --user-base`/bin"

The Installing Packages tutorial on python.org describes how to locate the binary directory:
On Windows
You can find the user base binary directory by running
python -m site --user-site and replacing site-packages with Scripts.
For example, this could return
C:\Users\Username\AppData\Roaming\Python36\site-packages so you
would need to set your PATH to include
C:\Users\Username\AppData\Roaming\Python36\Scripts.
On Linux and macOS
On Linux and macOS you can find the user base binary directory by
running python -m site --user-base and adding bin to the end. For
example, this will typically print ~/.local (with ~ expanded to the
absolute path to your home directory) so you’ll need to add
~/.local/bin to your PATH.

I stumbled upon this question because I created, successfully built and published a PyPI Package, but couldn't execute it after installation. The $PATHvariable was correctly set.
In my case the problem was that I hadn't set the entry_pointin the setup.py file:
entry_points = {'console_scripts':
['YOUR_CONSOLE_COMMAND=MODULE_NAME.FILE_NAME:FUNCTION_NAME'],},

On Windows, you need to add the path %USERPROFILE%\AppData\Roaming\Python\Scripts to your path.

Windows and Python 3.9 from MS Store
I have a different path with python -m site --user-base and python -m site - yes, the second command without --user-base to get all sites - as the other answers here state:
C:\Users\<your User>\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.9_qbz5n2kfra8p0\LocalCache\local-packages\Python39\site-packages
Why is my path different
Because I installed python from MS Store
Solution
Put the above path in your path and replace site-packages with scripts

When you install Python or Python3 using MacOS installer (downloaded from Python website) - it adds an exporter to your ~/.profile script. All you need to do is just source it. Restarting all the terminals should also do the trick.
WARNING - I believe it's better to just use pip3 with Python3 - for future benefits.
If you already have Python3 installed, the following steps work for me on macOS Mojave:
Install ansible first using sudo - sudo -H pip3 install ansible
you create a symlink to the Python's bin path
sudo ln -s /Library/Frameworks/Python.framework/Versions/Current/bin /Library/Frameworks/Python.framework/current_python_bin
and staple it to .profile
export PATH=$PATH:/Library/Frameworks/Python.framework/current_python_bin
run source ~/.profile and restart all terminal shells.
Type ansible --version

In addition to adding python's bin directory to $PATH variable, I also had to change the owner of that directory, to make it work. No idea why I wasn't the owner already.
chown -R ~/Library/Python/

I solve the problem!
Use pip3 instead pip.
pip3 install foobaz
vim ~/.zshrc and add:
export PATH="/Users/your_name/Library/Python/3.8/bin:$PATH"
source ~/.zshrc
Now MacOS has shifted the default terminal from bash to zsh. Therefore, you have to source zshrc but not bashrc or bash_profile.
foobaz -v

had the same issue with macOS Monterey. I had to modify my .bash_profile file and add the following entry
export PATH="~/Library/Python/3.8/bin:$PATH"
The default python version on macOS Monterey is 3.8, but you will have to double check your python version to make sure you're using the correct one