It’s finally time to get started with python 3. I’ve been putting it off for a while because of concerns that the libraries are not yet ready, that my code would require a lot of massaging, and pretty much because I dislike changing my practices. I like to make small changes instead of throwing the big switch and digging through lots and lots of problems.
Well after running into python 3 code at work and attending PyCon 2013 back in March I’m pretty convinced I just need to charge ahead. Fortunately for me it couldn’t be easier to set up python 3 and to get started.
I use homebrew for package management on my mac. I love it because it gives me access to all the great utilities I’m used to from Ubuntu and Debian with the advantages of having a mac as my personal machine. For me getting started was easy:
$ brew update
$ brew install python3
==> Downloading http://python.org/ftp/python/3.3.2/Python-3.3.2.tar.bz2
Already downloaded: /Library/Caches/Homebrew/python3-3.3.2.tar.bz2
==> ./configure --prefix=/usr/local/Cellar/python3/3.3.2 --enable-ipv6 --datarootdir=/usr/local/Cellar/python3/3.3.2/share --datadir=/usr/local/Cellar/python3/3.3.2/share --enable-fr
==> make
==> make install PYTHONAPPSDIR=/usr/local/Cellar/python3/3.3.2
==> make frameworkinstallextras PYTHONAPPSDIR=/usr/local/Cellar/python3/3.3.2/share/python3
==> Downloading https://pypi.python.org/packages/source/d/distribute/distribute-0.6.45.tar.gz
Already downloaded: /Library/Caches/Homebrew/distribute-0.6.45.tar.gz
==> /usr/local/Cellar/python3/3.3.2/bin/python3.3 -s setup.py install --force --verbose --install-scripts=/usr/local/Cellar/python3/3.3.2/bin --install-lib=/usr/local/lib/python3.3/s
==> 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/python3/3.3.2/bin/python3.3 -s setup.py install --force --verbose --install-scripts=/usr/local/Cellar/python3/3.3.2/bin --install-lib=/usr/local/lib/python3.3/s
==> Caveats
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
See: https://github.com/mxcl/homebrew/wiki/Homebrew-and-Python
==> Summary
/usr/local/Cellar/python3/3.3.2: 4699 files, 92M, built in 4.3 minutes
The next thing you probably want to do is try it out with a current project of yours. This is pretty easy if you head over to your project and create a virtual environment. I’ll show you two different ways. Assuming you have virtualenv already installed you can run this command which will correctly use python 3:
$ virtualenv env3 --python `which python3`
Using base prefix '/usr/local/Cellar/python3/3.3.2/Frameworks/Python.framework/Versions/3.3'
New python executable in env/bin/python3.3
Also creating executable in env/bin/python
Installing distribute.........done.
Installing pip................done.
The second and probably more straight forward way is simply to install a python 3 version of virtualenv. To do this you’ll end up using easy_install
$ easy_install-3.3 virtualenv
Searching for virtualenv
Reading http://pypi.python.org/simple/virtualenv/
Best match: virtualenv 1.9.1
Downloading https://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.9.1.tar.gz#md5=07e09df0adfca0b2d487e39a4bf2270a
Processing virtualenv-1.9.1.tar.gz
Writing /var/folders/wt/w5r4g27579n28673yx1ftjyr0000gn/T/easy_install-tt0yg7/virtualenv-1.9.1/setup.cfg
Running virtualenv-1.9.1/setup.py -q bdist_egg --dist-dir /var/folders/wt/w5r4g27579n28673yx1ftjyr0000gn/T/easy_install-tt0yg7/virtualenv-1.9.1/egg-dist-tmp-66fy1m
warning: no previously-included files matching '*' found under directory 'docs/_templates'
warning: no previously-included files matching '*' found under directory 'docs/_build'
Adding virtualenv 1.9.1 to easy-install.pth file
Installing virtualenv-3.3 script to /usr/local/bin
Installing virtualenv script to /usr/local/bin
Installed /usr/local/lib/python3.3/site-packages/virtualenv-1.9.1-py3.3.egg
Processing dependencies for virtualenv
Finished processing dependencies for virtualenv
$ virtualenv-3.3 env3
Using base prefix '/usr/local/Cellar/python3/3.3.2/Frameworks/Python.framework/Versions/3.3'
New python executable in env/bin/python3.3
Also creating executable in env/bin/python
Installing distribute.........done.
Installing pip................done.
Next you should activate the virtualenv and check the python version:
$ source env3/bin/activate
(env3) $ python --version
Python 3.3.2
One thing that might trip you up. When homebrew installed python 3 for you it helpfully makes a pip3 version for you. This is great if you’re using pip3 to install python packages globally. What might not be apparent is that inside your virtualenv the same executable is called pip. Since you are in a virtualenv you only need one version of it available, but in the global space where you have both python 2 & 3 installed its nice to be able to differentiate. Don’t worry, pip will indeed install python 3 related packages to your python 3 installation in your environment.
Now try to install something:
$ pip install ipython
...
$ pip freeze > requirements.txt
$ cat requirements.txt
distribute==0.6.34
ipython==0.13.2
In the future you can use that requirements.txt file to install packages:
$ pip install -r requirements.txt
This is a great way to version control all your package dependencies and help others install them when they check out your code.
Good luck with python 3 and I hope this article helped.