Python¶
According to wikipedia “Python is a widely used general-purpose, high-level programming language. Its design philosophy emphasizes code readability, and its syntax allows programmers to express concepts in fewer lines of code than would be possible in languages such as C++ or Java.”
Installation¶
This section shows how to install Python 2.7, how to use create virtual environments, how to install necessary libraries including windows specific libraries. If you want to use Jython/Python in the context of modelio (see Modelio) you do not have anything to install as Jython 2.7 is embedded into this tool.
Installing Python 2.7¶
Detailed information is available in the BeginnersGuide of python wiki.
On most unix systems python is usually installed so try python -V
on the
command line. If the version is >= 2.7.6 you can skip this step.
Note
There are two python ecosystems: python 2.X and 3.X. There some language differences between Python 2 and Python 3. Since not all libraries have been ported to 3.X Python 2 is still the most common choice when a lot of libraries are required.
Download Python 2.7.10. WARNING: On windows you must select the 32 bits version (web).
Install python in a directory like
%SCRIBESTOOLS%\Python27
. Keep the version number (at least 2.7) since it is common to have another directory like%SCRIBESTOOLS%\Python34
for Python 3.4.msiexec /i c:DOWNLOADSWinpython-2.7.10.msi TARGETDIR=%SCRIBESTOOLS%Python27 ALLUSER=1 ADDLOCAL=ALL
Change the two following directories to the PATH environment variable (if not already done by the installation program).
# replace ';' separator by ':' on unix # add %SCRIBESTOOLS%\Python2.7;%SCRIBESTOOLS%\Python2.7\Scripts to PATH
To test your installation, open a shell windows and type
python
. The python interpreter should open and you should be able to typeprint 'hello world'
for instance.quit()
will close the interpreter.
Virtual environments¶
Install virtualenvwrapper (or virtualenvwrapper-win on windows). This can be done with one command (according to your platform):
pip install virtualenvwrapper-win # on windows
pip install virtualenvwrapper # otherwise
Create a directory that will contains all virtual environments. For instance
%SCRIBESTOOLS%\PyVEnvs27
:
mkdir %SCRIBESTOOLS%\PyVEnvs27
Set the WORKON_HOME
environment variable to the directory just created and
don’t forget to open a new shell to see the effects of this change.:
# define WORKON_HOME variable as %SCRIBESTOOLS%\PyVEnvs27
Use a new shell to create a new virtual environment named ScribeEnv
:
mkvirtualenv ScribeEnv
# this creates a directory ``%SCRIBESTOOLS%\PyVEnvs27\ScribeEnv``.
# You should also see that the prompt of the shell is now prefixed with
# (ScribeEnv) like in the following line:
# (ScribeEnv) C:\Users\jmfavre>
This (ScribeEnv)
indicates that the python virtual environment used in
this shell is ScribeEnv
. This is valid only for this shell.
If you want to open another shell you will need to “activate” this
virtual environment:
workon ScribeEnv
From now on, you will have to activate the ScribeEnv virtual environment each time you open a new shell and want to use/install python software.
Libraries¶
Some python libraries depends on the OS (those who are using C libraries for instance). Select the section corresponding on your OS:
- installing Python libraries on windows.
- installing Python libraries on unix.
Libraries on windows¶
This section is devoted to installing python libraries on windows.
Native libraries¶
Note
Some python libraries need to be compiled with a C compiler. This is tricky on standard windows boxes. When a python library is not available for windows, a good idea is to look on the following web site: Unofficial Windows Binaries for Python Extension Packages.
pywin32¶
pywin32 is a set of python extensions for Windows. This library is required in particular by Scrapy.
download the 32 bits version
pywin32-219.win32-py2.7.exe
(web).do not click on the executable but type instead the following command (make sure that
(ScribeEnv)
is in the prompt):easy_install C:\DOWNLOADS\pywin32-219.win32-py2.7.exe
pygraphviz¶
pygraphviz is a python API to use the GraphViz graph package.
download
pygraphviz‑1.3rc2‑cp27‑none‑win32.whl
(web). This version works withgraphviz 2.38.msi
.do not click on the executable but type instead the following command (make sure that
(ScribeEnv)
is in the prompt):pip install c:\DOWNLOADS\pygraphviz-1.3rc2-cp27-none-win32.whl
Python libraries¶
To install regular python libraries (those that are based on python only)
type the following command (make sure that (ScribeEnv)
is in the prompt):
pip install XXXX\requirements-windows.txt
Libraries on Unix¶
This section is devoted to installing python libraries on unix.
Native libraries¶
On Ubuntu 14.04 the following native libraries have to be installed for python libraries to work properly.
Tip
For other unix systems try first to install the python libraries (see next section) and check on Google what to do if you got error messages.
sudo apt-get install autoconf g++ python2.7-dev python-dev
sudo apt-get build-dep python-imaging # for Pillow package
sudo apt-get install libjpeg8 libjpeg62-dev libfreetype6 libfreetype6-dev # for Pillow package
sudo apt-get install libffi-dev libssl-dev libxml2-dev libxslt1-dev
Python libraries¶
To install python libraries first download requirements-ubuntu.txt
.
Then change the path in the following command by the path to your virtualenv directory
(e.g. /usr/share/PyVEnvs27/ScribesEnv
) and type:
sudo /<path-to-yout-virtual-env>/bin/pip install requirements-ubuntu.txt
Documentation¶
The best way to find information about python is just to ask question such
as “python read file at once” on google. You may also want to have a
look at J/Python in a nutshell
and print a cheat sheet :