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virtualenv: command not found in Python

I am trying to create a new virtual environment for a tutorial. I have installed virtualenv and virtualenvwrapper multiple times but every time I try creating a new virtual environment my terminal displays - mkvirtualenv: command not found. When I try finding out the version of virtualenv it shows virtualenv: command not found. Something similar was happening with my pip installation as well but then it got resolved when I used some command.
I would like to point out that my PATH seems to be really messed up. The PATH is pointing to /Library/Frameworks/Python.framework/Versions/3.8/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Apple/usr/bin. Please help.
I saw something else when I use pip show virtualenv it gives me details of the version and the author but when I use virtualenv --version it sends a virtualenv: command not found.

First of all, you will need to install virtualenv as it is a python 2 external dependency.
pip install virtualenv
this will allow you to use virtualenv globally.
Alternatively, you can use from Python 3.5+
python -m virtualenv venv
However if you dont wish to support python 2 you can use venv which is installed on from python 3.3
python3 -v venv venv

Took quite some time to figure it out but what worked for me was to install it using pip3 install instead of pip install
pip3 install virtualenv

pip/python: normal site-packages is not writeable

I have a new Macbook - a user installed it, and then I installed a new user (mine), granted admin privileges and deleted the old one. I am on OS Catalina.
Since the installation I've been having several permission problems.
VSCode can't find Jupyter Notebook, pip installs packages at ~/Library/Python/3.7/site-packages.
When I do which python3 I get usr/bin/python3.
When I do pip3 install <package> I get: Defaulting to user installation because normal site-packages is not writeable And then it says it has already been installed, even though I can't access it when I do import <package>.
It's seems clear that this is a permission problem, pip can't install to the "base" python, and them python can't find what I've installed into ~/Library/Python/3.7/site-packages.
I've tried reinstalling the OS, but since I haven't done a clean install, it didn't change anything.
What am I missing?
How exactly can I fix permissions? Where do I want packages to be installed (venv sure, but some packages I want global (like jupyter).

As #TomdeGeus mentioned in the comments, this command works for me:
Python 3:
python3 -m pip install [package_name]
Python 2:
python -m pip install [package_name]

It's best to not use the system-provided Python directly. Leave that one alone since the OS can change it in undesired ways, as you experienced.
The best practice is to configure your own Python version(s) and manage them on a per-project basis using virtualenv (for Python 2) or venv, possibly via poetry, (for Python 3). This eliminates all dependency on the system-provided Python version, and also isolates each project from other projects on the machine.
Each project can have a different Python point version if needed, and gets its own site_packages directory so pip-installed libraries can also have different versions by project. This approach is a major problem-avoider.

python3.7 -m pip install [package_name]
(you should use the version that you have, of course)
solved it for me.
The most voted answer python3 -m pip install [package_name] does not help me here.
In my case, this was caused by a conflict with the dominating 3.6 version that was also installed as a default. You might ask yourself why you have 3.6 on your system, you will most probably not use that version now. The reason is that 3.6 is used as an independent default python version for many package installers. Those installers do not want to check which individual version you use and whether that fits, they just use 3.6 as a default, if you like it or not.
Here is a proof by example --upgrade pip:
pip3 install --upgrade pip
Defaulting to user installation because normal site-packages is not writeable
Requirement already satisfied: pip in
/home/USERNAME/.local/lib/python3.6/site-packages (20.3.1)
python3 -m pip install --upgrade pip
Defaulting to user installation because normal site-packages is not writeable
Requirement already satisfied: pip in
/home/USERNAME/.local/lib/python3.6/site-packages (20.3.1)
python3.7 -m pip install --upgrade pip
Collecting pip
Cache entry deserialization failed, entry ignored
Using cached https://files.pythonhosted.org/packages/ab/11/2dc62c5263d9eb322f2f028f7b56cd9d096bb8988fcf82d65fa2e4057afe/pip-20.3.1-py2.py3-none-any.whl
Installing collected packages: pip Successfully installed pip-20.3.1

I'm using Anaconda on Ubuntu and had the same problem.I fixed it by the following steps:
deactivating current environment
conda deactivate
Then, the base environment activates. I deactivated the base conda environment too. To do so, I used conda deactivate again.
Finally, I activate my project environment directly (instead of activating from the base environment) by the following command. Afterward, I installed the intended package successfully and worked perfectly.
conda activate myenv
pip install somepackage

sudo pip install
Worked for me. But pip install is not recommended to be run with sudo. The issue I was facing on BIGSUR was, it was using system python. Once I Installed python 3.9 using
brew install python#3.9
Then pip worked fine

For readers who thought themselves accidentally update system pip:
If you saw this info in your terminal output:
Defaulting to user installation because normal site-packages is not writeable
then you will be fine. Use the pip3 you just updated to run:
pyenv global system # since I use pyenv
pip3 uninstall pip # this one does the trick
Then you can check again pip3 --version will point to the original old (XCode/System-)pip. E.g. (2022/2/28):
pip 20.2.3 from /Applications/Xcode.app/Contents/Developer/Library/Frameworks/Python3.framework/Versions/3.8/lib/python3.8/site-packages/pip (python 3.8)

It occurs with me when I the virtual enviroment folder name was : venv.
in this case, It gives errors like :
No module pip
Default folder is unwritable
renaming the folder solve the proplem.

Check on the command line "which python" to see if it is the value you expect.
If you have a virtual environment activated, check /venv/bin/activate to see the value of VIRTUAL_ENV= and make sure it is the correct path . The path may be wrong if you renamed or moved the project. If the path is wrong, you can delete the venv and make a new one.

For me, none of the suggestions worked so I had to delete the current virtual environment folder venv and recreate it using one of the following commands:
python -m venv venv
python3 -m venv venv
Check the source of pip on Ubuntu 20.04
which pip
returns the correct path
/home/myname/fullstack/person_api/venv/bin/pip
UPDATE
I presume that some might encounter this problem because they set python path as environmental variable like this in ~/.bashrc:
python=/path/to/python
which you should not be doing! Instead we could do:
py=python
PATH=/path/to/python:$PATH
I bumped into this issue specifically because of this!

Had this same issue on a fresh install of Debian 9.12.
Rebooting my server solved the issue.

In my case on Linux, the ownership of the conda env directory had changed to another Linux user (long story), and so the the normal site-packages was not writeable due to a permissions issue.
The solution was to change ownership back to the user doing pip install.

I met exactly the same issue.
I just type sudo python3.8 -m pip install .... and the error disappeared.
If I remove the sudo, issue remains.

For those running on a Pi, that accidentally installed pip as root. Just chown the lib folder to the pi user:
sudo chown -R pi:pi /usr/local/lib/python3.9/

in my case python3 -m pip install [package_name] did not solve that.
in my case, it was a problem related to other processes occupying the directory.
I restart Pycharm and close any other program that might occupy this folder, and reinstalled the package in site-packages directory successfully.

When this problem occurred to me I have tried all the mentioned approaches but they don't seem to work.
Instead, restarting Python language server in my VSCode did the job - my SimPy package is now found. On Mac it is Cmd+Shift+P and select "Python: Restart Language Server".

Had similar issue on Ubuntu 20.04.4 LTS in VirtualBox, but none of the suggestions here worked for me.
I was trying to install open3d in a venv and every time I was getting
"Defaulting to user installation because normal site-packages is not writeable"
which at first I didn't even noticed. open3d was always being installed in /usr/bin/python3 environment. I've restarted the VM but without luck, so I guess the problem was not just missing write access.
So in VS Code, which was using the venv, importing open3d was not possible. But testing from terminal from the activated venv with python3 -c "import open3d as o3d; print(o3d.__version__)" was working fine and that confused me totally. I even broke my system pip installation using sudo, see further below if you want to know how to fix it.
Anyhow, the solution to my problem was to explicitly point to the python3 file in the venv where I wanted to install the package:
venv/bin/python3 -m pip install open3d
So I was testing out everything and eventually installed with sudo: sudo pip3 install open3d. This of course didn't solved the problem and open3d was still missing in the venv. Even worse, I got the message:
"WARNING: You are using pip version 21.3.1; however, version 22.0.4 is available.
You should consider upgrading via the '/usr/bin/python3 -m pip install --upgrade pip' command."
So I did it but with sudo, updating the system pip and then found out here that this is not good:
WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
Following an advice here, I tried to revert to original version, only then pip3 broke:
sudo pip3 uninstall pip
sudo pip3 --version
sudo: pip3: command not found
The apt package was still there:
sudo apt install python3-pip python3-pip is already the newest version
(20.0.2-5ubuntu1.6).
So I had to reinstalled to fix the problem:
sudo apt-get remove python3-pip
sudo apt install python3-pip

Maybe you have python, python3, pip or pip3 aliased. In that case pip might not work well anymore, as the alias isn't always available and so pip/pip3 might resolve python/python3 differently compared to in your terminal.
That could give rise to pip/pip3 trying to install in the system python, and that could give rise to your error.

I tried ever single recommendation described here. In every instance, I get the exact same result: SyntaxError: invalid syntax (<stdin>, line 1)
I'm not sure who designed the system like this, but it seems basically useless, based on my experience so far. Either create a system that works, or don't create anything at all.

Pipenv: Command Not Found

I'm attempting to use pipenv. I ran the command pip install pipenv, which ran successfully:
...
Successfully built pipenv pathlib shutilwhich pythonz-bd virtualenv-clone
Installing collected packages: virtualenv, pathlib, shutilwhich, backports.shutil-get-terminal-size, pythonz-bd, virtualenv-clone, pew, first, six, click, pip-tools, certifi, chardet, idna, urllib3, requests, pipenv
...
However, when I run the command pipenv install in a fresh root project directory I receive the following message: -bash: pipenv: command not found. I suspect that I might need to modify my .bashrc, but I'm unclear about what to add to the file or if modification is even necessary.

This fixed it for me:
sudo -H pip install -U pipenv

That happens because you are not installing it globally (system wide). For it to be available in your path you need to install it using sudo, like this:
$ sudo pip install pipenv

If you've done a user installation, you'll need to add the right folder to your PATH variable.
PYTHON_BIN_PATH="$(python3 -m site --user-base)/bin"
PATH="$PATH:$PYTHON_BIN_PATH"
See pipenv's installation instructions

I tried this:
python -m pipenv # for python2
python3 -m pipenv # for python3
Why this works: In Bash and other Unix-like shell environments, the -m option is used to specify a module to be run as a script.
When you run a Python script using the python -m command, you are telling the Python interpreter to execute the script as if it were a top-level module, rather than as a script file. The python -m pipenv command tells the Python interpreter to run the pipenv module as a script. The pipenv module must be importable from the current working directory or from one of the directories in the PYTHONPATH environment variable.

I have same problem with pipenv on Mac OS X 10.13 High Seirra, another Mac works just fine. I use Heroku to deploy my Django servers, some in 2.7 and some in 3.6. So, I need both 2.7 and 3.6. When HomeBrew install Python, it keeps python points to original 2.7, and python3 points to 3.6.
The problem might due to $ pip install pipenv. I checked /usr/local/bin and pipenv isn't there. So, I tried a full uninstall:
$ pip uninstall pipenv
Cannot uninstall requirement pipenv, not installed
You are using pip version 9.0.1, however version 10.0.1 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
$ pip3 uninstall pipenv
Skipping pipenv as it is not installed.
Then reinstall and works now:
$ pip3 install pipenv
Collecting pipenv

Where Python store packages
Before jumping into the command that will install pipenv, it is worth understanding where pip installs Python packages.
Global site-packages is where Python installs packages that will be available to all users and all Python applications on the system. You can check the global site package with the command
python -m site
For example, on Linux with Python 3.7 the path is usually
/usr/lib/python3.7/dist-packages/setuptools
User site-packages is where Python installs packages available only for you. But the packages will still be visible to all Python projects that you create. You can get the path with
python -m site --user-base
On Linux with Python 3.7 the path is usually
~/.local/lib/python3.7/site-packages
Using Python 3.x
On most Linux and other Unices, usually Python 2 and Python 3 is installed side-by-side. The default Python 3 executable is almost always python3. pip may be available as either of the following, depending on your Linux distribution
pip3
python3-pip
python36-pip
python3.6-pip
Linux
Avoid using pip with sudo! Yes, it's the most convenient way to install Python packages and the executable is available at /usr/local/bin/pipenv, but it also mean that specific package is always visible for all users, and all Python projects that you create. Instead, use per-user site packages instead with --user
pip3 install --user pipenv
pipenv is available at
~/.local/bin/pipenv
macOS
On macOS, Homebrew is the recommended way to install Python. You can easily upgrade Python, install multiple versions of Python and switch between versions using Homebrew.
If you are using Homebrew'ed Python, pip install --user is disabled. The global site-package is located at
/usr/local/lib/python3.y/site-packages
and you can safely install Python packages here. Python 3.y also searches for modules in:
/Library/Python/3.y/site-packages
~/Library/Python/3.y/lib/python/site-packages
Windows
For legacy reasons, Python is installed in C:\Python37. The Python executable is usually named py.exe, and you can run pip with py -m pip.
Global site packages is installed in
C:\Python37\lib\site-packages
Since you don't usually share your Windows devices, it is also OK to install a package globally
py -m pip install pipenv
pipenv is now available at
C:\Python37\Scripts\pipenv.exe
I don't recommend install Python packages in Windows with --user, because the default user site-package directory is in your Windows roaming profile
C:\Users\user\AppData\Roaming\Python\Python37\site-packages
The roaming profile is used in Terminal Services (Remote Desktop, Citrix, etc) and when you log on / off in a corporate environment. Slow login, logoff and reboot in Windows can be caused by a large roaming profile.

OSX GUYS, OVER HERE!!!
As #charlax answered (for me the best one), you can use a more dynamic command to set PATH, buuut for mac users this could not work, sometimes your USER_BASE path got from site is wrong, so you need to find out where your python installation is.
$ which python3
/usr/local/bin/python3.6
you'll get a symlink, then you need to find the source's symlink.
$ ls -la /usr/local/bin/python3.6
lrwxr-xr-x 1 root wheel 71 Mar 14 17:56 /usr/local/bin/python3.6 -> ../../../Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6
(this ../../../ means root)
So you found the python path (/Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6), then you just need to put in you ~/.bashrc as follows:
export PATH="$PATH:/Library/Frameworks/Python.framework/Versions/3.6/bin"

Installing pipenv globally can have an adverse effect by overwriting the global/system-managed pip installation, thus resulting in import errors when trying to run pip.
You can install pipenv at the user level:
pip install --user pipenv
This should install pipenv at a user-level in /home/username/.local so that it does not conflict with the global version of pip. In my case, that still did not work after running the '--user' switch, so I ran the longer 'fix what I screwed up' command once to restore the system managed environment:
sudo python3 -m pip uninstall pip && sudo apt install python3-pip --reinstall
^ found here: Error after upgrading pip: cannot import name 'main'
and then did the following:
mkdir /home/username/.local ... if it doesn't already exist
export PYTHONUSERBASE=/home/username/.local
Make sure the export took effect (bit me once during this process):
echo $PYTHONUSERBASE
Then, I ran the pip install --user pipenv and all was well. I could then run pipenv from the CLI and it did not overwrite the global/system-managed pip module. Of course, this is specific to the user so you want to make sure you install pipenv this way while working as the user you wish to use pipenv.
References:
https://pipenv.readthedocs.io/en/latest/diagnose/#no-module-named-module-name https://pipenv.readthedocs.io/en/latest/install/#pragmatic-installation-of-pipenv https://pip.pypa.io/en/stable/user_guide/#user-installs

I don't know what happened, but the following did the work (under mac os catalina)
$ brew install pipenv
$ brew update pipenv
after doing this i am able to use
$ pipenv install [package_name]

OS : Linux
Pip version : pip3
sudo -H pip3 install -U pipenv
OS : Windows
Pip version : any one
sudo -H pip install -U pipenv

For thse who installed it using sudo pip3 install pipenv, you need to use python3 -m pipenv shell or python3.9 -m pipenv shell

I'm using zsh on my Mac, what worked for me is at first install pipenv
pip3 install --user pipenv
Then I changed the PATH in the ~/.zshrc
vi ~/.zshrc
In the editor press i to insert your text:
export PATH="/Users/yourUser/Library/Python/3.9/bin:$PATH"
Press esc and then write :wq!
Close the terminal and re-open it.
And finally write pipenv
This way worked for me using macOS BigSur 11.1

On Mac you may have to do:
pip3 install pipenv
Then, cd into your root directory to locate the .zshrc file.
Then add this to path
export PATH=/Library/Frameworks/Python.framework/Versions/3.9/bin:$PATH
Note: 3.9 is the version of Python running on your system.
Note: You can access the .zshrc by using cmd + shift + .
in your root directory... the file is hidden by default
Save and restart your terminal

Fixed this easily by installing pipenv with my central package manager (apt)
sudo apt install pipenv
You could easily install pipenv using your package manager (apt, yum, brew) and it adds it directly to your $PATH variables.
More to mention is it works on zsh. I use zsh on Ubuntu and tried adding pipenv to $PATH and other solutions but didn't work till I used apt to install it.

HOW TO MAKE PIPENV A BASIC COMMAND
Pipenv with Python3 needs to be run as "$ python -m pipenv [command]" or "$ python3 -m pipenv [command]"; the "python" command at the beginning varies based on how you activate Python in your shell. To fix and set to "$ pipenv [command]": [example in Git Bash]
$ cd ~
$ code .bash_profile
The first line is necessary as it allows you to access the .bash_profile file. The second line opens .bash_profile in VSCode, so insert your default code editor's command.
At this point you'll want to (in .bash_profile) edit the file, adding this line of code:
alias pipenv='python -m pipenv'
Then save the file and into Git Bash, enter:
$ source .bash_profile
You can then use pipenv as a command anywhere, for example:
$ pipenv shell
Will work.
This method of usage will work for creating commands in Git Bash. For example:
alias python='winpty python.exe'
entered into the .bash_profile and:
$ source .bash_profile
will allow Python to be run as "python".
You're welcome.

On Mac OS X Catalina it appears to follow the Linux path. Using any of:
pip install pipenv
pip3 install pipenv
sudo pip install pipenv
sudo pip3 install pipenv
Essentially installs pipenv here:
/Users/mike/Library/Python/3.7/lib/python/site-packages/pipenv
But its not the executable and so is never found. The only thing that worked for me was
pip install --user pipenv
This seems to result in an __init__.py file in the above directory that has contents to correctly expose the pipenv command.
and everything started working, when all other posted and commented suggestions on this question failed.
The pipenv package certainly seems quite picky.

If you are on MAC
sudo -H pip3 install pipenv

For window users this may be due to conflicting installation with virtualenv. For me it worked when I uninstalled virtualenv and pipenv first, and then install only pipenv.
pip uninstall virtualenv
pip uninstall pipenv
pip install pipenv
Now pipenv install xxx worked for me

After installing pipenv (sudo pip install pipenv), I kept getting the "Command Not Found" error when attempting to run the pipenv shell command.
I finally fixed it with the following code:
pip3 install pipenv
pipenv shell

Here is how I successfully resolved "Pipenv: Command Not Found" on my Mac OSX
You should change the ownership of these directories to your user.
sudo chown -R $(whoami) /usr/local/share
make sure that your user has write permission.
chmod u+w /usr/local/share
Then Consider installing with Homebrew:
brew update
brew install pyenv

This simply solved it for me if you are on windows.
pip install pipenv
Second, replace your <username> in the following paths and add them to the PATH environment variable:
c:\Users\<username>\AppData\Roaming\Python\Python38\Site-Packages
C:\Users\<username>\AppData\Roaming\Python\Python38\Scripts
You need to close the Command Prompt and reopen it.
Third, type the following command to check if the pipenv installed correctly:
pipenv -h
I hope this helps you too!

In this case you just need to add the binary path to your bash. In case you're using ZSH for example you need to edit the.zshrc file as an admind and then add the code mentioned by #charlax on the comments above:
PYTHON_BIN_PATH="$(python3 -m site --user-base)/bin"
PATH="$PATH:$PYTHON_BIN_PATH"

You might consider installing pipenv via pipsi.
curl https://raw.githubusercontent.com/mitsuhiko/pipsi/master/get -pipsi.py | python3
pipsi install pew
pipsi install pipenv
Unfortunately there are some issues with macOS + python3 at the time of writing, see 1, 2. In my case I had to change the bashprompt to #!/Users/einselbst/.local/venvs/pipsi/bin/python

In some cases of old pip version:
sudo easy_install pip
sudo pip install pipenv

First check if pipenv is installed:
pipenv --version
If no version is available on your system, then run the following command to install pipenv
sudo aptitude install pipenv

first install pip using following command
pip3 install pipenv
Now check whether pipenv is showing by using following command
pipenv --version if you see like command not found: pipenv use following commands
Now we have to set the path for pipenv, to do that first we have to find the user base binary directory,
On linux and Mac we can do it as following
python3 -m site --user-base
this command will display something like this
/some_directory/Python/3.9
use the path displayed in your terminal and append /bin at the end, now your path looks like this
/some_directory/Python/3.9/bin
now you have to set the path, if you are using zsh (z shell) type nano ~/.zshrc in the terminal or if you are using code editor like VSCode and path is set for VScode type code ~/.zshrc
if you are using bash use nano ~/.bashrc or code ~/.bashrc
in the file at last add following line
export PATH="$PATH:/somedirectory/Python/3.9/bin"
save the file and exit the terminal
now open new terminal and type pipenv --version you should see something like pipenv, version 2022.10.25
on Windows we can do as following
python -m site --user-site
you should see something like
C:\Users\Username\AppData\Roaming\Python36\site-packages`
now replace site-packages with Scripts.
this could return
C:\Users\Username\AppData\Roaming\Python36\Scripts
You can set your user PATH permanently in the Control Panel. You may need to log out for the PATH changes to take effect.

It's probably installed in your user path.
for instance, if your user(username) is tom check this path
/home/tom/.local/bin/pipenv
if pipenv exists in the path you can move or copy it to the general user path, so you can execute pipenv from all terminal sessions.
cp /home/tom/.local/bin/pipenv /usr/bin/
then you should be able to run pipenv

For me, what worked on Windows was running Command Prompt as administrator and then installing pipenv globally: python -m pip install pipenv.

virtualenv does not include pip

I am trying to create a virtual environment using virtualenv on Mac OS X El Capitan. I have installed Python 2.7.11 with brew, which includes pip, wheel and setuptools by default.
Hovewer, when I try to install virtualenv following instructions in the documentation or from any other resource, I get several problems:
virtualenv executable is not placed in /usr/local/bin after pip makes its job, so I need to ln -s it by hand (it may indicate, that there is something wrong with installation on this step).
After I run virtualenv venv, it creates new environment, catches Python 2.7.11 from brew-installation, but: there is no pip inside bin folder. That means, that if I try which pip, having venv activated, it returns a global position of pip — /usr/local/bin/pip, not /path/to/venv/bin/pip.
As a consequence, installing packages inside venv uses global pip and installs them to a global sites-packages, not that inside venv, and it's quite the opposite of what environment should do.
Could you please suggest what may be wrong and how to fix it?
EDIT: The thing to mention is that I used to have other versions of Python installed on my computer, which I have recently deleted as it is described in this answer. Maybe it causes the issue, and some more thorough cleaning is needed.

Try removing or renaming the .pydistutils.cfg file in your home directory, e.g. by renaming with mv ~/.pydistutils.cfg ~/oldpydistutils.cfg
I'm putting a detailed answer here to help others, but the original credit goes to this answer. If you know what specifically in .pydistutils.cfg was causing the problem, let me know!
I was having the same issue: my virtual environments were created without a local copy of pip, although they had a local copy of python. This meant that using $ pip from within the virtual environment installed to the global package location, and was not visible to the environment's python.
How I diagnosed this on my machine:
I create a virtualenvironment with $ virtualenv env
Activated the virtual environment with $ source env/bin/activate
Checked python location: run (env)$ which python with output /Users/<username>/env/bin/python (as expected)
Checked pip location: run (env)$ which pip with output /usr/local/bin/pip (NOT expected)
To check where our packages are going, we can try to install a package in the virtual environment:
Try to install a package: (env)$ pip install HTTPServer which succeeds
Try to run the package: (env)$ python -m HTTPServer which fails with error /Users/emunsing/env/bin/python: No module named HTTPServer
To double-check, try to install again: (env)$ pip install HTTPServer which produces Requirement already satisfied (use --upgrade to upgrade): HTTPServer in /usr/local/lib/python2.7/site-packages
Double-checking, we see that there's no Pip in the environment's /bin folder:
$ ls env/bin
activate activate.fish python python2
activate.csh activate_this.py python-config python2.7
And so while the system finds the local python version, it can't find a local pip to use and traverses the $PATH. It ended up using pip from /usr/local/bin, leaving me unable to install packages locally to the virtual environment.
Here's what I tried:
- Reinstalling python brew uninstall python followed by brew upgrade and brew install python --build-from-source
- Installing pip using the get-pip.py command as described in the Pip documentation
Here's what I ruled out:
- I was not using sudo pip ... which caused similar problems in this other question and haven't done so at any time on this Python/pip install
- My virtual environment didn't show a local installation of pip, as was the case in these similar questions: This one for Windows, This one for Mac OS X.
Ultimately, I found that eliminating the ~/.pydistutils.cfg file fixed the problem, allowing for fresh virtual environments that had their own local pip. The contents of my ~/.pydistutils.cfg file were:
[global]
verbose=1
[install]
install-scripts=$HOME/bin
[easy_install]
install-scripts=$HOME/bin
Simply renaming the ~/.pydistutils.cfg file appears to fix the problem: it seems that although this file was created by the homebrew installation, some settings in this file may be incompatible with virtualenv. While removing this file hasn't had any bad effects on my system, you may need to use the --user flag when installing packages with pip to the global environment (e.g. $ pip install --user HTTPServer). Here are more details on .pydistutils.cfg if you want to work on tailoring it for your needs.

virtualenv executable is not placed in /usr/local/bin after pip makes its job, so I need to ln -s it by hand (it may indicate, that there is something wrong with installation on this step).
Don't do that. That will only hide the bug and not solve the problem. Here's a short guide how to debug this kind of issues:
Start with which -a python. The first path you see should be /usr/local/bin/python, if not check your PATH variable.
Next, check which -a pip. Again the first path should be /usr/local/bin/pip. If not, run python -m ensurepip and recheck.
Now install virtualenv using pip install virtualenv, after that check the output of which -a virtualenv. The first path should be /usr/local/bin/virtualenv, if not check the output of env |grep PYTHON for unexpected environment variables.
Finally check the output of virtualenv --version to make sure you have the latest version.

I had the issue when running virtualenv: "ImportError: No module named pip."
My solution was to downgrade virtualenv. I had 16.2.0.
pip uninstall virtualenv
pip install virtualenv==15.1.0

Just hit same issue on Linux. Seems like there are multiple causes of this issue, but for me answer was to remove ~/.pip/.
Details: I had this in my .pip/pip.conf for some reason I can't remember:
$ cat ~/.pip/pip.conf
[global]
use_https = True
index = https://pypi.python.org/pypi
prefix = /home/sam/local/
and was using local versions on Python, Pip installed at ~/local/. For some reason virtualenv installed pip must pick up prefix = /home/sam/local/ setting and pip was being installed there.

Try this: sudo apt install pythonV.v-distutils.
In my case V.v == 3.8.
This worked for me.

Support doesn't work

I'm trying to use neovim with deoplete and UtilSnips. Both requires Python support from nvim.
I followed the instructions in :help nvim_python to set the support but the output of :echo has('python') or :echo has('python3') are both 0.
On nvim-startup I get the message UltiSnips requires py >= 2.7 or py3 and for deoplete It requires Neovim with Python 3 support ("+python3").
My python (2.7.10) and python3 (3.4.3) are both installed with homebrew. The neovim module is installed over pip and pip3 with install neovim but nvim can't find it, even when I set the let g:python_host_prog path in nvimrc.
I don't know what I am able to do anymore, has anyone an idea whats wrong with it?

Please follow the instruction on https://neovim.io/doc/user/provider.html#provider-python to setup the python interpreter for neovim.
First, install pynvim (previously, it was named neovim, but that has been changed) plugin
pip3 install pynvim
Print g:loaded_python3_provider
echo g:loaded_python3_provider
" for python 2.x use the following
" echo g:loaded_python_provider
If it returns 1, the python is not setup for neovim. In your ~/.config/nvim/init.vim file, set the python interpreter
let g:python3_host_prog='/path/to/python3'
" for python2, use the following instead
"let g:python_host_prog = '/path/to/python2.7'

I encountered the same problem lately. Here are the steps adapted from answer of #VforVitamin where I made it working.
Assuming python2 and python3 are installed.
Install neovim plugin pip3 install neovim.
Open neovim.
Execute command :UpdateRemotePlugins.
Restart neovim.

I had the issue myself because I used neovim inside virtualenv. If so, make sure to pip install neovim inside your virtualenv, and make sure that import neovim works in the python interpreter.
If that doesn't help, you can try and run neovim with debug messages (neovim -V3, or any other logging level) and see what you can pick from there.

I bet you have a line in your init file that starts with "set runtimepath=".
Change it to "set runtimepath+="

If when you try
let [interp, errors] = provider#pythonx#Detect(2)
From the docs at
https://github.com/neovim/neovim/wiki/Troubleshooting#python-support-isnt-working
You get errors, could be that you have your VIM environment variable pointed to the wrong (probably vim74) runtime directory.
Neovim needs pythonx.vim from the runtime/autoload/providers/ folder to load a python interp. Vim74 doesn't provide this file.
If you have an env. variable of VIM (with a path), it will use that as your location of your runtime files - I had my set to /usr/share/vim/vim74, changing it to the location of neovim worked. I guess there is a compile time option to point to the correct location too.

I was with the same problem and the solution actually cames from the question.
What I did was:
pip install --upgrade pip
pip3 install --upgrade pip
sudo pip install setuptools
sudo pip3 install setuptools
sudo pip install neovim
sudo pip3 install neovim
After it, enter in neovim and :UpdateRemotePlugins. Close it and open again.
After these steps I had neovim working properly.
Edit:
For those using Arch Linux, we have a peculiarity about Python. The steps are:
Install pip (python3) and pip2 (python2): pacman -S python-pip python2-pip
Instead of pip3, you should use pip2
Beyond this minor difference, the rest of commands work pretty much the same way.

As pointed out by #fwalch, the documentation has changed to https://neovim.io/doc/user/provider.html#provider-python.
Neovim comes shipped with Python3 enabled, but you need to install the pynvim module in order to use Neovim Python3 plugins:
python3 -m pip install --user --upgrade pynvim