[파이썬] 파이썬 여러 버전 설치하기; virtualenv 사용하기.

source: http://bhfsteve.blogspot.kr/2012/05/run-multiple-python-versions-on-your.html

파이썬 여러 버전 사용하기

파이썬 2.7은 기본적으로 설치되어 있다고 가정

steve@ubuntu64 ~ $ sudo add-apt-repository ppa:fkrull/deadsnakes

steve@ubuntu64 ~ $ sudo apt-get update

steve@ubuntu64 ~ $ sudo apt-get install python2.4 python2.5 python2.6

이제 2.4 2.5 2.6 2.7이 모두 설치된 상태가 된다. 이 상태에서 python이라고 치면 여전히 2.7이 켜진다.

왜냐하면 python은 심볼릭링크이며 python2.7을 가리키기 때문. 

steve@ubuntu64 ~ $ python
Python 2.7.3 (default, Apr 20 2012, 22:39:59) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

steve@ubuntu64 ~ $ ls -l /usr/bin/python*
lrwxrwxrwx 1 root root       9 Apr 17 13:20 /usr/bin/python -> python2.7
lrwxrwxrwx 1 root root       9 Apr 17 13:20 /usr/bin/python2 -> python2.7
-rwxr-xr-x 1 root root 1216520 May 21 12:13 /usr/bin/python2.4
-rwxr-xr-x 1 root root 1403624 May  3 00:17 /usr/bin/python2.5
-rwxr-xr-x 1 root root 2652056 May 12 08:43 /usr/bin/python2.6
-rwxr-xr-x 1 root root 2993560 Apr 20 19:37 /usr/bin/python2.7

따라서 2.5버전을 실행하려면 아래와 같이 명시적인 버전을 함께 쓰면 된다.

steve@ubuntu64 ~ $ python2.5
Python 2.5.6 (r256:88840, May  3 2012, 04:16:14) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> 

내가 2.6을 주로 사용하고자 한다해도  python 심볼릭링크를 수정하지는 말자. 내부적인 의존성 문제를 일으킬 가능성이 있다.  (This is a point of interest.  I would not mess with the symbolic link.  Ubuntu runs python for many internal maintenance scripts and those scripts are expecting the python version that shipped with ubuntu.)

Use virtualenv to manage your python installations and package sets

So now that you have multiple versions of python on your system, how to manage them?  How do you keep packages installed for one version separate from packages installed for another.  What if you want to run one version of django for client X and a different version for client Y?

That's where virtualenv comes in.  If your a ruby programmer, this is analogous to rvm.  Virtualenv lets you manage the python versions and package installations separately for different projects or clients.

Installing virtualenv is simple

As always, you're just a single apt-get command away from having virtualenv ready to go:

steve@ubuntu64 ~ $ sudo apt-get install python-virtualenv

That it.  Virtualenv is ready to go now.

Quick example

Say your starting a new project for a client.  They are running python2.5 and want to use the mocks, nose and coverage packages for testing.  Here a walkthrough of how to use virtualenv to manage the project.

First, let's create a directory for the project:

steve@ubuntu64 ~ $ mkdir -p ~/dev/project1
steve@ubuntu64 ~ $ cd ~/dev/project1

Next, run virtualenv to create the environment for the project:


steve@ubuntu64 ~/dev/project1 $ virtualenv -p /usr/bin/python2.5 .env
Running virtualenv with interpreter /usr/bin/python2.5
New python executable in .env/bin/python2.5
Also creating executable in .env/bin/python
Installing distribute.............................................................................................................................................................................................done.
Installing pip...............done.
steve@ubuntu64 ~/dev/project1 $ 

This command tells virtualenv to create a .env directory and to place a copy of the 2.5version of python in it.  This copy of the 2.5 python is brand-spankin' new.  It doesn't have any packages (beyond the standard library) installed.  You will need to install them yourself.  Any packages that you install in this instance of python will not be available to main python installation or other virtualenv instances.

Before your can use this new copy, you need to activate it:


steve@ubuntu64 ~/dev/project1 $ source .env/bin/activate
(.env)steve@ubuntu64 ~/dev/project1 $

The activate script manipulates your path environment variable, placing the new python instance first in your path.  This makes is so that when you run python, it will use the version from your instance:


(.env)steve@ubuntu64 ~/dev/project1 $ which python
/home/steve/dev/project1/.env/bin/python
(.env)steve@ubuntu64 ~/dev/project1 $ python
Python 2.5.6 (r256:88840, May  3 2012, 04:16:14) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>

Also, notice that your prompt starts with (.env).  This tells you that you're running with the virtualenv instance activated.  To install packages in your instance, use the pipcommand:


(.env)steve@ubuntu64 ~/dev/project1 $ pip install mock nose coverage
Downloading/unpacking mock
  Downloading mock-0.8.0.tar.gz (749Kb): 749Kb downloaded
  Running setup.py egg_info for package mock
    warning: no files found matching '*.png' under directory 'docs'
    warning: no files found matching '*.css' under directory 'docs'
    warning: no files found matching '*.html' under directory 'docs'
    warning: no files found matching '*.js' under directory 'docs'
Downloading/unpacking nose
  Downloading nose-1.1.2.tar.gz (729Kb): 729Kb downloaded
  In the tar file /tmp/pip-dH_WYa-unpack/nose-1.1.2.tar.gz the member nose-1.1.2/doc/doc_tests/test_selector_plugin/support/tests/mymodule/my_function$py.class is invalid: 'filename None not found'
  In the tar file /tmp/pip-dH_WYa-unpack/nose-1.1.2.tar.gz the member nose-1.1.2/doc/doc_tests/test_restricted_plugin_options/restricted_plugin_options.rst.py3.patch is invalid: 'filename None not found'
  Running setup.py egg_info for package nose
Downloading/unpacking coverage  Downloading coverage-3.5.2.tar.gz (115Kb): 115Kb downloaded
  Running setup.py egg_info for package coverage
    no previously-included directories found matching 'test'Installing collected packages: mock, nose, coverage
  Running setup.py install for mock
    warning: no files found matching '*.png' under directory 'docs'
    warning: no files found matching '*.css' under directory 'docs'
    warning: no files found matching '*.html' under directory 'docs'
    warning: no files found matching '*.js' under directory 'docs'
  Running setup.py install for nose
    Installing nosetests script to /home/steve/dev/project1/.env/bin
    Installing nosetests-2.5 script to /home/steve/dev/project1/.env/bin
  Running setup.py install for coverage
    building 'coverage.tracer' extension
    gcc -pthread -fno-strict-aliasing -DNDEBUG -g -fwrapv -O2 -Wall -Wstrict-prototypes -fPIC -I/usr/include/python2.5 -c coverage/tracer.c -o build/temp.linux-x86_64-2.5/coverage/tracer.o
    coverage/tracer.c:3:20: fatal error: Python.h: No such file or directory
    compilation terminated.
    **
    ** Couldn't install with extension module, trying without it...
    ** SystemExit: error: command 'gcc' failed with exit status 1
    **
    no previously-included directories found matching 'test'
    Installing coverage script to /home/steve/dev/project1/.env/bin
Successfully installed mock nose coverage
Cleaning up...
(.env)steve@ubuntu64 ~/dev/project1 $

To see that the packages have been installed, simply use them:




(.env)steve@ubuntu64 ~/dev/project1 $ python
Python 2.5.6 (r256:88840, May  3 2012, 04:16:14) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import mock
>>> import nose
>>> import coverage
>>>

When you're done working on the project, deactivate it.  You can always come back later and activate it again.


(.env)steve@ubuntu64 ~/dev/project1 $ deactivate
steve@ubuntu64 ~/dev/project1 $


Notice that when you deactivate the environment, your packages are no longer available:


steve@ubuntu64 ~/dev/project1 $ python
Python 2.7.3 (default, Apr 20 2012, 22:39:59) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import mock
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named mock
>>> import nose
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named nose
>>> import coverage
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named coverage
>>>

You can create as many virtualenv environments as you like.  I create one for each project that I work on.

Bonus material

To make life even easier, here's a couple additional things I do that you might find helpful!

First, once you've started to use virtualenv with some frequency, you start to get tired of downloading and installing the same packages over and over.  Pip has the ability to cache your downloaded packages for reuse.  To do that, you'll need to create a directory to store the download packages in:

steve@ubuntu64 ~ $ mkdir ~/.pip_download_cache

Then you'll need to set a variable to inform pip of the new directory.  Add the following to your .bashrc file:

export PIP_DOWNLOAD_CACHE=/home/steve/.pip_download_cache

Now when you do a pip install, it will keep the downloaded files in the ~/.pip_download_cache directory.  The next time you do a pip install of the same package, it will just use the copy from the directory instead of downloading it again.


Second, it can be tedious to always have to type 'source .env/bin/activate' every time you want to activate an environment.  Since I always put my virtual environments in a .env directory I can count on the command to activate always being the same.  So I create an alias for it.  I added the the following to my ~/.bash_aliases file:

alias activate='source .env/bin/activate'

Now once I cd into the projects directory, I simply type activate to activate my virtual environment.