If you want to install Python 3 using Homebrew:

brew install python3

Output:

==> Downloading http://python.org/ftp/python/3.3.0/Python-3.3.0.tar.bz2
Already downloaded: /Library/Caches/Homebrew/python3-3.3.0.tar.bz2
==> ./configure --prefix=/usr/local/Cellar/python3/3.3.0 --enable-ipv6 --datarootdir=/usr/local/Cell
==> make
==> make install PYTHONAPPSDIR=/usr/local/Cellar/python3/3.3.0
==> make frameworkinstallextras PYTHONAPPSDIR=/usr/local/Cellar/python3/3.3.0/share/python3
==> Downloading https://pypi.python.org/packages/source/d/distribute/distribute-0.6.35.tar.gz
Already downloaded: /Library/Caches/Homebrew/distribute-0.6.35.tar.gz
==> /usr/local/Cellar/python3/3.3.0/bin/python3.3 -s setup.py install --force --verbose --install-li
==> Downloading https://pypi.python.org/packages/source/p/pip/pip-1.3.1.tar.gz
Already downloaded: /Library/Caches/Homebrew/pip-1.3.1.tar.gz
==> /usr/local/Cellar/python3/3.3.0/bin/python3.3 -s setup.py install --force --verbose --install-li
==> Caveats
Homebrew's Python3 framework
  /usr/local/Cellar/python3/3.3.0/Frameworks/Python.framework

Distribute and Pip have been installed. To update them
  pip3 install --upgrade distribute
  pip3 install --upgrade pip

To symlink "Idle 3" and the "Python Launcher 3" to ~/Applications
  `brew linkapps`

You can install Python packages with
  `pip3 install <your_favorite_package>`

They will install into the site-package directory
 /usr/local/lib/python3.3/site-packages
Executable python scripts will be put in:
 /usr/local/share/python3
so you may want to put "/usr/local/share/python3" in your PATH, too.

    See: https://github.com/mxcl/homebrew/wiki/Homebrew-and-Python

Once installed update your system PATH variable, add the next line to the ~/.bash_profile file:

export PATH=/usr/local/bin:/usr/local/sbin:~/bin:$PATH

And then:

source ~/.bash_profile

Now launch Python:

python3

Output:

Python 3.3.0 (default, Mar 26 2013, 10:01:40)
[GCC 4.2.1 Compatible Apple LLVM 4.2 (clang-425.0.27)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

You can check the python3 path:

which python3

Output:

/usr/local/bin/python3

For Apple silicon machines, the paths are slightly different. After running brew install python, you must ensure your ~/.zshrc file uses the correct Homebrew paths:

# Homebrew
eval "$(/opt/homebrew/bin/brew shellenv)"

# Homebrew: Python
export PATH="/opt/homebrew/opt/python/libexec/bin:$PATH"

Results:

% which python
/opt/homebrew/opt/python/libexec/bin/python

% python --version
Python 3.9.9

% which pip
/opt/homebrew/opt/python/libexec/bin/pip

% pip -V
pip 21.3.1 from /opt/homebrew/lib/python3.9/site-packages/pip (python 3.9)

Brew's Python interpreter changed its location again and I had to update my ~/.zshrc file to:

export PATH="$(brew --prefix)/opt/python@3/libexec/bin:$PATH"

There isn't a .../opt/python/... anymore which is annoying, because now I have to specify v3 explicitly, but at least better than having to specify the minor version like in the comments.

My Background

I had this same problem, and I think it may have arisen after upgrading to OSX 10.11 (El Capitan). When trying to run pip, I got -bash: pip: command not found I also tried python -m pip which did not work either (no module found). Trying to unlink and relink python through Homebrew did not work.

The Fix

I was able to fix the problem by completely uninstalling and reinstalling python via Homebrew.

brew uninstall python && brew install python

If you want to remove older versions of python too, use

brew uninstall --force python && brew install python

None of my existing pip installs were affected, and are all still listed when I run pip freeze. After the reinstall, the binary is now symlinked to /usr/local/bin/pip, which did not exist before. Strangely, the actual binary in /usr/local/Cellar/python/2.7.11/bin/pip did not exist before the reinstall either.

Did you try to invoke /usr/local/Cellar/python3/3.6.5_1/bin/pip3 ? If it works, it means pip installation has been successfuly completed and your bashfile will be wrong. However, the bashfile looks normal for me.

Did you confirm that there is pip3 in /usr/local/Cellar/python3/3.6.5_1/bin/? If it does not exist, pip is not installed in the first place.

It seems to have the same problem with this page ("pip3 not installed with python 3.4.2 #33897").
The questioner of "pip3 not installed with python 3.4.2 #33897" have finaly solved it by removing /private/var/folders/hy/l_6wd1ps0nz835v4g41zhhtr0000gn/T/pip_build.
It may be because of Brew had failed to complete pip installation.

First, to bootstrap the pip installer, hit python3 -m ensurepip --upgrade and python -m ensurepip. If it won't work, try to hit python3 -m ensurepip -vvv -U and tell what do it say.

Install Python3 with Brew Enter brew command into terminal

brew install python3

Optional, PATH environment Set up PATH environment variable, if you used HomeBrew to install Python3, then HomeBrew already added PATH.

Do not change PATH environment if you can launch python3 from terminal.

Add the following line to your ~/.profile file

export PATH=/usr/local/bin:/usr/local/sbin:$PATH

Usually your Python installation directory looks like this, add it to your PATH

PATH="/Library/Frameworks/Python.framework/Versions/3.6/bin:${PATH}"