We were at La Cantine on May 21th 2012 in Paris for the "PyCon.us Replay session".
La Cantine is a coworking space where hackers,
artists, students and so on can meet and work. It also organises some
meetings and conferences about digital culture, computer science, ...
On May 21th 2012, it was a dev day about Python. "Would you
like to have more PyCon?" is a french wordplay where PyCon sounds like Picon, a french "apéritif" which
traditionally accompanies beer. A good thing because the meeting began at 6:30
PM! Presentations and demonstrations were about some Python projects presented
at PyCon 2012 in Santa Clara (California) last
March. The original pycon presentations are accessible on pyvideo.org.
By Gael Pasgrimaud (@gawel_).
pdb is the well-known Python
debugger. Gael showed us how to easily use this almost-mandatory tool when you
develop in Python. As with the gdb debugger, you can stop the execution at a
breakpoint, walk up the stack, print the value of local variables or modify
temporarily some local variables.
The best way to define a breakpoint in your source code, it's to write:
import pdb; pdb.set_trace()
Insert that where you would like pdb to stop. Then, you can step trough the code with
s, c or n commands. See help for more information. Following, the
help command in pdb command-line interpreter:
(Pdb) help
Documented commands (type help <topic>):
========================================
EOF bt cont enable jump pp run unt
a c continue exit l q s until
alias cl d h list quit step up
args clear debug help n r tbreak w
b commands disable ignore next restart u whatis
break condition down j p return unalias where
Miscellaneous help topics:
==========================
exec pdb
It is also possible to invoke the module pdb when you run a Python script such
as:
$> python -m pdb my_script.py
By Alexis Metereau (@ametaireau).
Pyramid is an open
source Python web framework from Pylons Project. It concentrates on providing
fast, high-quality solutions to the fundamental problems of creating a web
application:
- the mapping of URLs to code ;
- templating ;
- security and serving static assets.
The framework allows to choose different approaches according the
simplicity//feature tradeoff that the programmer need. Alexis, from the French team of Services Mozilla,
is working with it on a daily basis and seemed happy to use it. He told us that
he uses Pyramid more as web Python library than a web framework.
By Benoit Chesneau (@benoitc).
Circus is a process watcher and
runner. Python scripts, via an API, or command-line interface can be used to
manage and monitor multiple processes.
A very useful web application, called circushttpd, provides a way to
monitor and manage Circus through the web. Circus uses zeromq, a well-known tool used at
Logilab.
This session was a well prepared and funny live demonstration by Julien
Tayon of matplotlib, the Python 2D plotting library . He showed us some quick and easy stuff.
For instance, how to plot a sinus with a few code lines with matplotlib and
NumPy:
import numpy as np
import matplotlib.pyplot as plt
fig = plt.figure()
ax = fig.add_subplot(111)
# A simple sinus.
ax.plot(np.sin(np.arange(-10., 10., 0.05)))
fig.show()
which gives:
You can make some fancier plots such as:
# A sinus and a fancy Cardioid.
a = np.arange(-5., 5., 0.1)
ax_sin = fig.add_subplot(211)
ax_sin.plot(np.sin(a), '^-r', lw=1.5)
ax_sin.set_title("A sinus")
# Cardioid.
ax_cardio = fig.add_subplot(212)
x = 0.5 * (2. * np.cos(a) - np.cos(2 * a))
y = 0.5 * (2. * np.sin(a) - np.sin(2 * a))
ax_cardio.plot(x, y, '-og')
ax_cardio.grid()
ax_cardio.set_xlabel(r"$\frac{1}{2} (2 \cos{t} - \cos{2t})$", fontsize=16)
fig.show()
where you can type some LaTeX equations as X label for instance.
The force of this plotting library is the gallery of several examples with
piece of code. See the matplotlib gallery.
Dimitri Merejkowsky reviewed how Python can be used to control and program Aldebaran's humanoid robot NAO.
Unfortunately, Olivier Grisel who was supposed to make three interesting presentations
was not there. He was supposed to present :
- A demo about injecting arbitrary code and monitoring Python process with
Pyrasite.
- Another demo about Interactive Data analysis with Pandas and the new IPython
NoteBook.
- Wrap up : Distributed computation on cluster related project:
IPython.parallel, picloud and Storm + Umbrella
Thanks to La Cantine and the different organisers for this friendly dev day.
