A4 portrait - PET: Python Entre Todos - Python Argentina

Context managers 10
Context managers
Concluding, destructors are useful, comfortable, and hard to predict. They have to be
used with care, and whenever assuming that destructors are called with any
immediate quality after dereferencing an instance, we’ll be creating code that only
works properly on CPython.
For reliable file closing, Python provides us with a better, more predictable and more
uniformly supported tool: the with statement:
>>> with open("archivito.txt", "r") as f:
... # do something
... # no need to call f.close(),
... # it's called automatically when exiting the 'with' block
We won’t go into the with statement, but it’s worth mentioning that it doesn’t
replace destructors. Only the use we’ve been giving them along this article, that is, to
close files. The with statement also has many more uses, so I invite you to do some
research yourselves.
Painless Concurrency: The multiprocessing Module
Author: Roberto Alsina
The author has been around python for a while, and is finally getting
the hang of it.
Blog: http://lateral.netmanagers.com.ar
twitter: @ralsina
identi.ca: @ralsina
Sometimes when you are working on a program you run into one of the classic
problems: your user interface blocks. We are performing some long task and the
window “freezes”, jams, doesn’t update until the operation is over.
Sometimes we can live with it, but in general it gives the image of amateurish, or
badly written application.
The traditional solution for this problem is making your program multi threaded, and
run more than one parallel thread. You pass the expensive operation to a secondary
thread, do what it takes so the application looks alive, wait until the thread ends, and
move on.
Here is a toy example:
# -*- coding: utf-8 -*-
import threading
import time
def trabajador():
print "Starting to work"
time.sleep(2)
print "Finished working"
def main():
print "Starting the main program"
thread = threading.Thread(target=trabajador)
print "Launching thread"
PET: English Translation (Issue 1, August 2010) — http://revista.python.org.ar