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How to Install Python 3 and PyDev on OSX

Here is a quick tour on how to setup an effective dev environment for Python 3 on your beloved OSX.

  1. Installing Homebrew
  2. Installing Python 3
  3. Installing Eclipse
  4. Installing PyDev for Eclipse

1. Installing Homebrew

There are many package installers on OSX but I find Homebrew very pleasant, simple and convenient. Homebrew, originally started by Max Howell, simplify the installation of open source tools (like ImageMagick, wget, ack etc..) that are not by default on OSX.

What I really like with Homebrew is that everything is installed on a directory that is not conflicting with the system directories. By default, it’s on /usr/local but you can change to whatever you like.

Installing Homebrew is very simple; open a Terminal window and type

ruby -e "$(curl -fsSkL raw.github.com/mxcl/homebrew/go)"

Once installed, just type brew in a terminal to check that Homebrew is installed. There are few commands to remember:

Type brew doctor and if the output is Your system is raring to brew, everything is ok. You can have more information on the Homebrew wiki.

2. Installing Python 3

To install Python 3 with Homebrew, simply type

brew install python3

Once Python 3 is installed, we’re going to check that is it ready to use or our system by launching the interactive console

python3

And you should see

$ python3
Python 3.3.0 (default, Feb  1 2013, 22:09:55) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 

Type Ctrl+D to exit the interpreter. It’s interesting to note that python launch the default 2.7 python interpreter and python3 is launching the 3.3 python interpreter.

Now that we have Python 3 installed on our system, we are going to install a package. Python 3 comes with pip. You should pay attention to which pip you are using:

The two package managers don’t share their site-package directory. If you want a python package x for both pythons, you need to install it twice. Once via pip for Python 2.7 and once via pip3 for python 3.3.

If we want to install SQLAlchemy for instance, type

pip3 install sqlalchemy

Then launch the python3 interactive console and test that SQLAlchemy is installed now

$ python3
Python 3.3.0 (default, Feb  1 2013, 22:09:55) 
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sqlalchemy
>>> 

No error, everything is OK! Note that, with Homebrew, Python 3 packages are installed under /usr/local/lib/python3.3/site-packages.

3. Installing Eclipse

Now that we have Python 3 installed, we can use any good text editor to write some code. It can be also useful, but not mandatory, to use a complete IDE with Python autocompletion, debugging facilities and so on. To do so, we’re going to install Eclipse and PyDev.

To install Eclipse, go to http://www.eclipse.org/downloads/, choose Mac OSX (Cocoa) and download Eclipse Classic 4.2.1. Untar the downloaded file and copy the eclipse directory under Applications.

4. Installing PyDev for Eclipse

PyDev is a Python IDE for Eclipse. To install it, launch Eclipse, go to ’Help > Install New Software’ (you can also follow these steps on PyDev online documentation)

PyDev installation step 1

Click on ’Add…’ then PyDev in ’Name’ and http://pydev.org/updates/ in ’Location’

PyDev installation step 2

Tap on ’OK’, then select PyDev in the combo box ’Work with:’

PyDev installation step 3

’Next’, select ’PyDev for Eclipse’, accept the Terms & Conditions, then ’Finish’.

Then accept the certificates and wait for Eclipse to restart.

After installing, we are going to configure PyDev to use our Python 3 interpreter.

  1. Go to ’Eclipse > Preferences > PyDev > Interpreter - Python’
  2. Select ’New’, in ’Interpreter Name’ set python3 and in ’Interpreter Executable’ set ’/usr/local/bin/python3’ (which is a symlink to /usr/local/Cellar/python3/3.3.0/Frameworks/Python.framework/Versions/3.3/bin/python3.3) then ’OK’

PyDev installation step 4 3. Just type OK on this window

PyDev installation step 5

Now, PyDev is configured and ready to use in Eclipse. To test it, go to ’File > New > Project…’ and select ’PyDev Project’, name your new project ’Test’, Project Type to ’Python’, Grammar Version to ’3.0’, interpreter to ’python3’, select ’Create ’src’ folder and add it to the PYTHONPATH’ and ’Finish’

PyDev installation step 6

Once the project is created, you can see on the left the PyDev Package Explorer with the Test project. Select the src folder, ’File > New > File’ and call it test.py. Copy/paste this code

if __name__ == ’__main__’:
    print(’Hello World’)

An run it from Eclipse (Run > Run). You can see the output directly in the Eclipse console. That’s all, you’re ready to code and debug! If you want to go further, check out the PyDev online documentation, it’s really good and complete.

From jc.

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