Apt-Get Install for Different Python Versions

apt-get install for different python versions

Python has got its own package managing facilities, in parallel to the one sets by the Linux distributions (including Ubuntu). The repository is the Pypi - Python Package Index, and packages are installed with pip or the easy_install script, which is part of Python's setuptools package.

As a rule of thumb, you should not use both the packages installed via pip/setuptools, and packages available to your distro (via apt-get, yum, urpmi, etc...) as they might conflict.

So, one of the less error prone way to deal with it is to have separate Python installs in your system - leave the python that came with the system for system scripts and such - on this python, make use of packages installed by your package manager only. And install other versions of Python (or even the same), to be run with "virtualenv"s - on these other install you install things with pip/setuptools only.

(And even if one opt to live boldly and not use virtualenvs, installing another python version on the same prefix (/usr, and even /usr/local) than your system's Python is a source to confusing errors and conflicts).

Note that the Debian - and Ubuntu - systems devised a way to run parallel official Python's in /usr, and to have apt-get to install Python packages to both Python versions at once. This mostly works, but they mess with Python's default directory hierarchy, and some applications fail to use Python in this way. (It is also a mess to find the module files themselves in a Debian or Ubuntu). So the above method apply as a recommendation even if your system do have more than one version of Python available on apt-get.

In short, once you have compiled your desired version of Python, do this:

1. use your system's package manager to install "python-setuptools" and "python-virtualenv" (not sure if these are the actual package names).
2. Use virtualenv to create an environment from which you will use your different Python version
3. Activate your virtualenv, and install Python packages using pip on it.

Virtualenv does feature a "--help" switch to help you, but you basically do:

$ virtualenv -p <path-to-python-interpreter>  <environment-dir>
$ source <environment-dir>/bin/activate

And there you are - all things using Python will "see" the interpreter in the virtualenv, due to environment variables set.

Install a module using pip for specific python version

Use a version of pip installed against the Python instance you want to install new packages to.

In many distributions, there may be separate python2.6-pip and python2.7-pip packages, invoked with binary names such as pip-2.6 and pip-2.7. If pip is not packaged in your distribution for the desired target, you might look for a setuptools or easyinstall package, or use virtualenv (which will always include pip in a generated environment).

pip's website includes installation instructions, if you can't find anything within your distribution.

Dealing with multiple Python versions and PIP?

The current recommendation is to use python -m pip, where python is the version of Python you would like to use. This is the recommendation because it works across all versions of Python, and in all forms of virtualenv. For example:

# The system default python:
$ python -m pip install fish

# A virtualenv's python:
$ .env/bin/python -m pip install fish

# A specific version of python:
$ python-3.6 -m pip install fish

Previous answer, left for posterity:

Since version 0.8, Pip supports pip-{version}. You can use it the same as easy_install-{version}:

$ pip-2.5 install myfoopackage
$ pip-2.6 install otherpackage
$ pip-2.7 install mybarpackage

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EDIT: pip changed its schema to use pipVERSION instead of pip-VERSION in version 1.5. You should use the following if you have pip >= 1.5:

$ pip2.6 install otherpackage
$ pip2.7 install mybarpackage

Check https://github.com/pypa/pip/pull/1053 for more details

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References:

• https://github.com/pypa/pip/issues/200
• http://www.pip-installer.org/docs/pip/en/0.8.3/news.html#id4
  
  https://pip.pypa.io/en/stable/news/#v0-8 or
  
  https://web.archive.org/web/20140310013920/http://www.pip-installer.org:80/docs/pip/en/0.8.3/news.html#id4

Multiple Python versions on the same machine?

I think it is totally independent. Just install them, then you have the commands e.g. /usr/bin/python2.5 and /usr/bin/python2.6. Link /usr/bin/python to the one you want to use as default.

All the libraries are in separate folders (named after the version) anyway.

If you want to compile the versions manually, this is from the readme file of the Python source code:

Installing multiple versions

On Unix and Mac systems if you intend to install multiple versions of Python
using the same installation prefix (--prefix argument to the configure
script) you must take care that your primary python executable is not
overwritten by the installation of a different version. All files and
directories installed using "make altinstall" contain the major and minor
version and can thus live side-by-side. "make install" also creates
${prefix}/bin/python3 which refers to ${prefix}/bin/pythonX.Y. If you intend
to install multiple versions using the same prefix you must decide which
version (if any) is your "primary" version. Install that version using
"make install". Install all other versions using "make altinstall".

For example, if you want to install Python 2.5, 2.6 and 3.0 with 2.6 being
the primary version, you would execute "make install" in your 2.6 build
directory and "make altinstall" in the others.

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