pyenv on mac

Homebrew in macOS
Update homebrew and install pyenv:
brew update
brew install pyenv
If you want to install (and update to) the latest development head of Pyenv rather than the latest release, instead run:
brew install pyenv --head
Then follow the rest of the post-installation steps, starting with Set up your shell environment for Pyenv.
OPTIONAL. To fix brew doctor's warning ""config" scripts exist outside your system or Homebrew directories"
If you're going to build Homebrew formulae from source that link against Python like Tkinter or NumPy (This is only generally the case if you are a developer of such a formula, or if you have an EOL version of MacOS for which prebuilt bottles are no longer provided and you are using such a formula).
To avoid them accidentally linking against a Pyenv-provided Python, add the following line into your interactive shell's configuration:
Bash/Zsh:
alias brew='env PATH="${PATH//$(pyenv root)\/shims:/}" brew'
Fish:
alias brew="env PATH=(string replace (pyenv root)/shims '' \"\$PATH\") brew"

B. Set up your shell environment for Pyenv
The below setup should work for the vast majority of users for common use cases. See Advanced configuration for details and more configuration options.
Bash
Stock Bash startup files vary widely between distributions in which of them source which, under what circumstances, in what order and what additional configuration they perform. As such, the most reliable way to get Pyenv in all environments is to append Pyenv configuration commands to both .bashrc (for interactive shells) and the profile file that Bash would use (for login shells).
First, add the commands to ~/.bashrc by running the following in your terminal:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc
echo 'eval "$(pyenv init - bash)"' >> ~/.bashrc
Then, if you have ~/.profile, ~/.bash_profile or ~/.bash_login, add the commands there as well. If you have none of these, create a ~/.profile and add the commands there.
to add to ~/.profile:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.profile
echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.profile
echo 'eval "$(pyenv init - bash)"' >> ~/.profile
to add to ~/.bash_profile:
echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bash_profile
echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bash_profile
echo 'eval "$(pyenv init - bash)"' >> ~/.bash_profile
Bash warning: There are some systems where the BASH_ENV variable is configured to point to .bashrc. On such systems, you should almost certainly put the eval "$(pyenv init - bash)" line into .bash_profile, and not into .bashrc. Otherwise, you may observe strange behaviour, such as pyenv getting into an infinite loop. See #264 for details.
Zsh
  echo 'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.zshrc
  echo '[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.zshrc
  echo 'eval "$(pyenv init - zsh)"' >> ~/.zshrc
If you wish to get Pyenv in noninteractive login shells as well, also add the commands to ~/.zprofile or ~/.zlogin.
Fish
If you have Fish 3.2.0 or newer, execute this interactively:
  set -Ux PYENV_ROOT $HOME/.pyenv
  fish_add_path $PYENV_ROOT/bin
Otherwise, execute the snippet below:
  set -Ux PYENV_ROOT $HOME/.pyenv
  set -U fish_user_paths $PYENV_ROOT/bin $fish_user_paths
Now, add this to ~/.config/fish/config.fish:
  pyenv init - fish | source
C. Restart your shell
for the PATH changes to take effect.
exec "$SHELL"

Virtual Environments and Packages

 

12.1. Introduction

Python applications will often use packages and modules that don’t come as part of the standard library. Applications will sometimes need a specific version of a library, because the application may require that a particular bug has been fixed or the application may be written using an obsolete version of the library’s interface.

This means it may not be possible for one Python installation to meet the requirements of every application. If application A needs version 1.0 of a particular module but application B needs version 2.0, then the requirements are in conflict and installing either version 1.0 or 2.0 will leave one application unable to run.

The solution for this problem is to create a virtual environment, a self-contained directory tree that contains a Python installation for a particular version of Python, plus a number of additional packages.

Different applications can then use different virtual environments. To resolve the earlier example of conflicting requirements, application A can have its own virtual environment with version 1.0 installed while application B has another virtual environment with version 2.0. If application B requires a library be upgraded to version 3.0, this will not affect application A’s environment.

12.2. Creating Virtual Environments

The module used to create and manage virtual environments is called venv. venv will usually install the most recent version of Python that you have available. If you have multiple versions of Python on your system, you can select a specific Python version by running python3 or whichever version you want.

To create a virtual environment, decide upon a directory where you want to place it, and run the venv module as a script with the directory path:

python -m venv tutorial-env

This will create the tutorial-env directory if it doesn’t exist, and also create directories inside it containing a copy of the Python interpreter and various supporting files.

A common directory location for a virtual environment is .venv. This name keeps the directory typically hidden in your shell and thus out of the way while giving it a name that explains why the directory exists. It also prevents clashing with .env environment variable definition files that some tooling supports.

Once you’ve created a virtual environment, you may activate it.

On Windows, run:

tutorial-env\Scripts\activate.bat

On Unix or MacOS, run:

source tutorial-env/bin/activate

(This script is written for the bash shell. If you use the csh or fish shells, there are alternate activate.csh and activate.fish scripts you should use instead.)

Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, and modify the environment so that running python will get you that particular version and installation of Python. For example:

$ source ~/envs/tutorial-env/bin/activate
(tutorial-env) $ python
Python 3.5.1 (default, May  6 2016, 10:59:36)
  ...
>>> import sys
>>> sys.path
['', '/usr/local/lib/python35.zip', ...,
'~/envs/tutorial-env/lib/python3.5/site-packages']
>>>

To deactivate a virtual environment, type:

deactivate

into the terminal.

12.3. Managing Packages with pip

You can install, upgrade, and remove packages using a program called pip. By default pip will install packages from the Python Package Index. You can browse the Python Package Index by going to it in your web browser.

pip has a number of subcommands: “install”, “uninstall”, “freeze”, etc. (Consult the Installing Python Modules guide for complete documentation for pip.)

You can install the latest version of a package by specifying a package’s name:

(tutorial-env) $ python -m pip install novas
Collecting novas
  Downloading novas-3.1.1.3.tar.gz (136kB)
Installing collected packages: novas
  Running setup.py install for novas
Successfully installed novas-3.1.1.3

You can also install a specific version of a package by giving the package name followed by == and the version number:

(tutorial-env) $ python -m pip install requests==2.6.0
Collecting requests==2.6.0
  Using cached requests-2.6.0-py2.py3-none-any.whl
Installing collected packages: requests
Successfully installed requests-2.6.0

If you re-run this command, pip will notice that the requested version is already installed and do nothing. You can supply a different version number to get that version, or you can run python -m pip install --upgrade to upgrade the package to the latest version:

(tutorial-env) $ python -m pip install --upgrade requests
Collecting requests
Installing collected packages: requests
  Found existing installation: requests 2.6.0
    Uninstalling requests-2.6.0:
      Successfully uninstalled requests-2.6.0
Successfully installed requests-2.7.0

python -m pip uninstall followed by one or more package names will remove the packages from the virtual environment.

python -m pip show will display information about a particular package:

(tutorial-env) $ python -m pip show requests
---
Metadata-Version: 2.0
Name: requests
Version: 2.7.0
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: me@kennethreitz.com
License: Apache 2.0
Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
Requires:

python -m pip list will display all of the packages installed in the virtual environment:

(tutorial-env) $ python -m pip list
novas (3.1.1.3)
numpy (1.9.2)
pip (7.0.3)
requests (2.7.0)
setuptools (16.0)

python -m pip freeze will produce a similar list of the installed packages, but the output uses the format that python -m pip install expects. A common convention is to put this list in a requirements.txt file:

(tutorial-env) $ python -m pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
requests==2.7.0

The requirements.txt can then be committed to version control and shipped as part of an application. Users can then install all the necessary packages with install -r:

(tutorial-env) $ python -m pip install -r requirements.txt
Collecting novas==3.1.1.3 (from -r requirements.txt (line 1))
  ...
Collecting numpy==1.9.2 (from -r requirements.txt (line 2))
  ...
Collecting requests==2.7.0 (from -r requirements.txt (line 3))
  ...
Installing collected packages: novas, numpy, requests
  Running setup.py install for novas
Successfully installed novas-3.1.1.3 numpy-1.9.2 requests-2.7.0

pip has many more options. Consult the Installing Python Modules guide for complete documentation for pip. When you’ve written a package and want to make it available on the Python Package Index, consult the Python packaging user guide.