Develop Reference

Python3 running on Mac but no Pip3?

I need to get pip3 running on my Mac terminal for a project. I have python3 installed, and I can run it, but when I try to run pip3 freeze, it says my command is not found.
I thought it would be automatically installed when I installed Python3. I tried to sudo install it, but it still didn't do anything. What can I do?

Besides brew install pip3, in case brew is not installed on your Mac, you can install pip3 via get_pip.py which can be found here. Assuming that python3 is already installed, cd to the directory where you saved get_pip.py and run the file with python3 get_pip.py. This should get pip3 installed on your machine.

On my MacBook Pro (10.13.5), which pip3 shows that it is located at /opt/local/bin/pip3 but it is a symlink to /opt/local/Library/Frameworks/Python.framework/Versions/3.6/bin/pip3.
This is the location of python3 if you installed it via MacPorts. If you installed it with HomeBrew, then it would be /usr/local/Cellar/python/3.7.0/bin/pip3 (again, version might vary).
Finding pip3
What I would do if I were you is first find out where your pip3 actually is by either using locate or trying to manually find it by typing (Change 3.6 to whatever version you're on.) either:
$ /opt/local/Library/Frameworks/Python.framework/Versions/3.6/bin/pip3 --version
or:
$ /usr/local/Cellar/python/3.7.0/bin/pip3 --version
You should see something like:
pip 9.0.3 from /opt/local/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages (python 3.6)
Otherwise, use locate:
$ locate pip3
As a last resort, the slow find can also be useful:
$ sudo find / -name pip3
Build a Symlink
Then, make a symbolic link to that file in a path that is in your $PATH (again, ensure you replace the first path with the path to your actual pip3):
$ sudo ln -s /opt/local/Library/Frameworks/Python.framework/Versions/3.6/bin/pip3 /opt/local/bin/pip3

Assuming you are using Python 3.4 or later in which pip is included by default, try the following command:
python3 -m pip freeze
When you use the -m command-line flag, python will search sys.path for the named module and execute its contents as the __main__ module. (more here)
This solution will allow you to use pip by python3 -m pip, but in order to use pip3 directly you can:
Install it via Homebrew:
brew install pip3
Install it with get-pip.py:
curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
python get-pip.py

You could try brew install pip3. Or check where pip is installed, that might point to Python 3's version.

Problems of VirtualEnv and pip3

I used VirtualEnv to create a python2 environment without system site packages like this:
virtualenv -p /usr/bin/python2.7 --no-site-packages ENV2.7
And I want to install packages in this environment.
However, I found that my python code is still trying to look for packages out of this environment.
For example, after activate this env, I used:
pip install matplotlib
And in my demo.py, there is
import matplotlib
But this raised an error, and can not find this package
However, when I use python in the terminal and enter the interactive python, import matplotlib dose not raise an error.
Then I started another terminal and tried to install this package out of the environment by pip3:
pip3 install matplotlib
It turned out that my demo.py just work well.
Any idea? Many Thanks!

It sounds like your virtualenv pip version may be using pip3 instead of pip2:
Make sure you are using the correct python version in your project that you mean to, and using the same version of pip in your virtualenv. (Note that you use pip above once, then you used pip3 outside your virtualenv.)
Check your pip version from inside the virtualenv:
workon (your env name)
which pip
pip -V
Output should look something like:
$ which pip
/home/yourname/.virtualenvs/testenv/bin/pip
$ pip -V
pip 9.0.1 from /home/yourname/.virtualenvs/testenv/local/lib/python2.7/site-packages (python 2.7)
It should tell you you're using pip inside your virtualenv, and the correct python version.
If that looks correct, install your packages.
pip install (whatever)
Check they are installed with pip freeze.
Run your project. :)

Using pip on Windows installed with both python 2.7 and 3.5

I am using Windows 10. Currently, I have Python 2.7 installed. I would like to install Python 3.5 as well. However, if I have both 2.7 and 3.5 installed, when I run pip, how do I get the direct the package to be installed to the desired Python version?

You will have to use the absolute path of pip.
E.g: if I installed python 3 to C:\python35, I would use:
C:\> python35\Scripts\pip.exe install packagename
Or if you're on linux, use pip3 install packagename
If you don't specify a full path, it will use whichever pip is in your path.

Because usually i change my intepreter to run something(i got 2 diff projects with both 2 and 3), i use these solution:
Add path to the environment as usual (of course)
Rename ur python.exe , in my case i want to run python 3 using command python3 on my cmd. So i renamed my python.exe in python3.x directory with python3. Itll works with python 2 ofc.
Then to use pip in both python, i use this command.
python3 -m pip install 'somepackage'
and to run pip on python2
python -m pip install 'somepackage'
This is may not the best solution out there, but i like this one
** WINDOWS **
ref : https://datascience.com.co/how-to-install-python-2-7-and-3-6-in-windows-10-add-python-path-281e7eae62a

In my case, I have Python 2.7 and Python 3.4, with the Python Launcher for Windows.
This is the output when running this commands:
PS C:\> pip -V
pip 9.0.1 from c:\python27\lib\site-packages (python 2.7)
PS C:\> pip3 -V
pip 9.0.1 from C:\Python34\lib\site-packages (python 3.4)
I'll note that in my Python27\Scripts\ directory, I have pip.exe, pip2.exe and pip2.7.exe.
And in my Python34\Scripts\ directory, I have pip.exe, pip3.exe and pip3.4.exe.
So all of these .exe files help you when you have different versions of Python installed at the same time.
Of course, for this to work, you have to have the respective Scriptsdirectries in your Path system enviroment variable.

The answer from Farhan.K will work. However, I think a more convenient way would be to rename python35\Scripts\pip.exe to python35\Scripts\pip3.exe assuming python 3 is installed in C:\python35.
After renaming, you can use pip3 when installing packages to python v3 and pip when installing packages to python v2. Without the renaming, your computer will use whichever pip is in your path.

I would advise against ever calling any pip script directly (nor pip3, pip2.7.exe, anything like that).
Instead, a surefire way is to always prefer the explicit variant of calling pip's executable module for a specific Python interpreter:
path/to/pythonX.Y -m pip somecommand
path/to/venv/bin/python -m pip somecommand
C:\path\to\venv\Scripts\python.exe -m pip somecommand
There are many advantages to this, for example:
It is explicit for which Python interpreter the projects will be pip-installed (Python 2 or 3, inside the virtual environment or not, etc.)
For a virtual environment, one can pip-install (or do other things) without activating it: path/to/venv/bin/python -m pip install SomeProject
Under Windows this is the only way to safely upgrade pip itself path\to\venv\Scripts\python.exe -m pip install --upgrade pip
But yes, if all is perfectly setup, then python3 -m pip install SomeProject and pip3 install SomeProject should do the exact same thing, but there are way too many cases where there is an issue with the setup and things don't work as expected and users get confused (as shown by the many questions about this topic on this platform).
References
Brett Cannon's article "Why you should use python -m pip"
pip's documentation section on "Upgrading pip"
venv's documentation section on "Creating virtual environments": "You don’t specifically need to activate an environment [...]"

I ran across an issue with running pip with absolute path. This might be related to WinPython's installation routine and the order of installing Python 3.6 first, 2.7 second, or Python 3.6 being in the path.
No matter which pip was called, it was activating the 3.6 one:
λ C:\prog\WinPython-64bit-2.7.13.1Zero\python-2.7.13.amd64\Scripts\pip2.exe --version
pip 9.0.1 from C:\prog\WinPython-64bit-3.6.1.0Zero\python-3.6.1.amd64\lib\site-packages (python 3.6)
What finally did the trick was calling pip as a module of the respective python binary:
λ C:\prog\WinPython-64bit-2.7.13.1Zero\python-2.7.13.amd64\python.exe -m pip --version
pip 9.0.1 from C:\prog\WinPython-64bit-2.7.13.1Zero\python-2.7.13.amd64\lib\site-packages (python 2.7)
Hope that might help someone with similar issues.

I tried many things , then finally
pip3 install --upgrade pip worked for me as i was facing this issue since i had both python3 and python2.7 installed on my system.
mind the pip3 in the beginning and pip in the end.
And yes you do have to run in admin mode the command prompt and make sure if the path is set properly.

1-open command prompt and change direction using the command cd C:\Python35\Scripts
2- write the command pip3 install --upgrade pip
3- close the command prompt and reopen it again to return to the default direction and use the command pip3.exe install package_name to install any package you want

How to override the pip command to Python3.x instead of Python2.7?

I am using OSX and I have pip installed for both Python3.5 and Python2.7. I know I can run the command pip2 to use Python2 and when I use the command pip3 Python3.x will be used.
The problem is that the default of pip is set to Python2.7 and I want it to be Python3.x.
How can I change that?
edit:
No, I am not running a virtual environment yet. If it was a virtual environment I could just run Python3.x and forget all about Python2.7, unfortunately since OSX requires Python2.7 for it's use I can't do that. Hence why I'm asking this.
Thanks for the answer. I however don't want to change what running python does. Instead I would like to change the path that running pip takes. At the moment pip -V shows me pip 8.1.2 from /Library/Python/2.7/site-packages (python 2.7), but I am looking for pip 8.1.2 from /Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages (python 3.5) I am sure there has to be a way to do this. Any ideas?

Run this:
pip3 install --upgrade --force pip
or even more explicit:
python3 -m pip install --upgrade --force pip
This will install pip for Python 3 and make Python 3 version of pip default.
Validate with:
pip -V

I always just run it via Python itself, this way:
python3 -m pip install some_module
or
python2 -m pip install some_module
The -m calls the __main__.py module of a specified package. Pip supports this.

Can't you alias pip='pip3' in your ~/.bash_profile?
In Terminal, run nano ~/.bash_profile, then add a line to the end that reads alias pip='pip3'. This is safe; it won't affect system processes, only your terminal.

For your projects, you should be using a virtualenv.
You can choose which python will be that of the virtualenv at creation time, by specifying it on the command line:
virtualenv -p python3 env
# then
. env/bin/activate
python # ← will run python3
That python interpreter will be the one used when you run python or pip while the virtualenv is active.
Under the hood, activating the virtualenv will:
modify your PATH environment setting so binaries in env/bin
override those from your system.
modify your PYTHONHOME
environment setting so python modules are loaded from env/lib.
So python, pip and any other package you install with pip will be run from the virtualenv, with the python version you chose and the package versions you installed in the virtualenv.
Other than this, running python without using virtualenv will just run the default python of the system, which you cannot usually change as it would break a lot of system scripts.

It works for me:
As super-user
Uninstall pip
sudo pip uninstall pip
Install pip
sudo python3 -m pip install --upgrade --force pip
Check install path
sudo pip -V
As local-user
Uninstall pip
pip uninstall pip
Install pip
python3 -m pip install --upgrade --force pip
Check install path
pip -V

Although PEP 394 does not specifically mention pip, it does discuss a number of other Python-related commands (including python itself). The short version is that, for reasons of backwards compatibility, the unversioned commands should refer to Python 2.x for the immediate future on most reasonable systems.
Generally, these aliases are implemented as symbolic links, and you can just flip the symlink to point at the version you want (e.g. with ln -f -s $(which pip3) $(which pip) as root). But it may not be a good idea if you have any software that expects to interact with Python 2 (which may be more than you think since a lot of software interacts with Python).
The saner option is to set up a Virtualenv with Python 3. Then, within the Virtualenv, all Python-related commands will refer to 3.x instead of 2.x. This will not break the system, unlike the previous paragraph which could well break things.

Since you have specified in the comments you want syntax like pip install [package] to work, here is a solution:
Install setuptools for Python3: apt-get install python3-setuptools
Now pip for Python3 could be installed by: python3 -m easy_install pip
Now you can use pip with the specific version of Python to
install package for Python 3 by: pip-3.2 install [package]

Why not just repoint the link /bin/python to python3? It seems like the easiest solution. Especially if you want it for all users of your system.

Pip suddenly using wrong version of Python

Having a weird problem with pip on os x.
As far as I can recall (and a quick look at my .bash_history seems to confirm) I have not made any recent changes to my configuration. Alas, the pip command seems to be suddenly using a different version of python than it was previously. Up until now I was using the command pip to manage my python2 libraries and pip3 to manage by python3 libraries. Suddenly, any attempts at running pip install fails with errors like missing parenthesis around print statements.
Here is the result of a few commands I attempted to figure out the problem:
which pip > /usr/local/bin/pip
which pip3 > /usr/local/bin/pip3
which python > /usr/local/bin/python
python version > Python 2.7.11
pip --version > pip 8.1.1 from /usr/local/lib/python3.5/site-packages (python 3.5)
So for some reason the pip command seems to be running from the PyPi2 database but in python3 now? Any ideas how to fix this?

I run with multiple Python versions and thus multiple pip versions as well.
Everytime, however, you update pip, you'll replace the standard pip command with the version you updated. So even pip3 install --upgrade pip will put a /usr/local/bin/pip in your system, messing up the Python 2 version.
Instead, I run pip as an (executable) module:
python3 -m pip search <package>
or
python2 -m pip search <package>
or even
python3.5 -m pip search <package>
This guarantees that your pip version always matches the Python version you want to use it for. It's somewhat longer to type, but I prefer the expliciteness of it (which, I guess, follows the Zen of Python).
Note that updating pip:
python3.5 -m pip install --upgrade pip
will still install a Python 3.5 version in /usr/local/bin/pip, but I'm simply ignoring that. Just beware of (shell) scripts that execute pip directly.

Find absolute path to Python you'd like to use:
which python
Open your default pip executable script:
vi $(which pip)
You will see a shebang line at the top which may point to wrong Python (i had that once too).
Point to the Python you want (see step 1), e.g.:
#!/usr/local/bin/python3.7

Try setting aliases by running the following commands in Terminal,
alias pip="/usr/local/bin/pip"
alias pip2="/usr/local/bin/pip"
alias pip3="/usr/local/bin/pip3"
If this solves your problem then you need to add the aliases in your bash profile.
Look How do I create a Bash alias? for more info.
Alternatively, you have to reinstall pip using python2 get-pip.py first and then python3 get-pip.py get-pip.py can be downloaded here https://bootstrap.pypa.io/get-pip.py

I had exactly the same problem!
I reinstall python2 by brew brew reinstall python#2
after reinstall, pip install packagename works!

None of these worked for me so what I did was navigate to
C:\Users(User)\AppData\Local\Programs\Python\
and deleted all the old python versions I wasn't using. (Worked)