If it won't be simple, it simply won't be. [source code] by Miki Tebeka, CEO, 353Solutions

Friday, November 30, 2007

Going Scheme Style

Lets count the words our code, omitting comments:
#!/usr/bin/env python

from functools import partial
import re

filter_comment = partial(re.compile("#.*$").sub, "")
words = re.compile("[^ \t\n\r]+").findall

def num_words(text):
'''Return the number of words in a code segment, ignoring comments

>>> num_words("")
0
>>> num_words("1 + 1")
3
>>> num_words("1 + 1 # add 1 to 1")
3
'''
return sum(map(len,
map(words,
map(filter_comment,
text.splitlines()))))


if __name__ == "__main__":
import doctest
doctest.testmod()

Friday, November 16, 2007

Word Reduction

A little solution to http://ddj.com/cpp/202806370?pgno=3:
#!/usr/bin/env python

DICTIONRAY = set()

def load_dictionary(filename):
DICTIONRAY.add("a")
DICTIONRAY.add("i")
for line in open(filename):
DICTIONRAY.add(line.strip())

def _reduction(word):
if word not in DICTIONRAY:
return []
if len(word) == 1:
return [word]

for i in range(len(word)):
subword = "%s%s" % (word[:i], word[i+1:])
if subword not in DICTIONRAY:
continue
path = reduction(subword)
if path:
return [word] + path
return []

CACHE = {}
def reduction(word):
if word not in CACHE:
CACHE[word] = _reduction(word)

return CACHE[word]

def main(argv=None):
if argv is None:
import sys
argv = sys.argv

from os.path import isfile
from optparse import OptionParser

parser = OptionParser("usage: %prog DICTIONRAY")

opts, args = parser.parse_args(argv[1:])
if len(args) != 1:
parser.error("wrong number of arguments") # Will exit

dictfile = args[0]
if not isfile(dictfile):
raise SystemExit("error: can't find %s" % dictfile)

load_dictionary(dictfile)
for word in sorted(DICTIONRAY, key=lambda w: len(w), reverse=1):
path = reduction(word)
if path:
print "\n".join(path)
break

if __name__ == "__main__":
main()
Works fast enough as well (running on SIGNLE.TXT):
mtebeka@bugs:word-reduction - 08:43 $ time ./word_reduction.py dictionaries/SINGLE.TXT
restraint's
restraints
restrains
retrains
retains
retain
retin
rein
rin
in
n

real 0m4.088s
user 0m4.023s
sys 0m0.065s
mtebeka@bugs:word-reduction - 08:43 $

Wednesday, October 31, 2007

Quick Web Searches

A little script to search the documents in Journal of Machine Learning.

import webbrowser
from urllib import urlencode

def jmlr(words):
query = "site:http://jmlr.csail.mit.edu filetype:pdf " + " ".join(words)
url = "http://www.google.com/search?" + urlencode([("q", query)])

webbrowser.open(url)

if __name__ == "__main__":
from optparse import OptionParser

parser = OptionParser("usage: %prog WORD1 [WORD2 ...]")

opts, args = parser.parse_args()
if not args:
parser.error("wrong number of arguments") # Will exit

jmlr(args)

I have many more is these for Google search, Wikipedia search, Acronym Search ...
The trick is to do a search using the web interface and then look at the URL of the results page.

Tuesday, October 23, 2007

Minimal testing

I'm using py.test as our test suite. And found out that even the most minimal tests give me great benefits:
def test_joke():
pass
One I have that in a file call test_joke.py,
py.test will pick it up and try to run it.

The good thing to have only this minimal code is that the test will fail if you happen to introduce a syntax error or some error in the module initialization.

Of course, when I have more time I beef up the tests ;)

What make it even more useful is a continuous integration system that run the tests every time someone checks in the code.

Wednesday, October 10, 2007

Persistant ID generator

Let's say you want to map key->number, and every time you get a new key you give it a different number.
(Useful for mapping words to vector index in IR)

The easy way is:
from collections import defaultdict
from itertools import count

vector_index = defaultdict(count(0).next)
print vector_index["a"] # 0
print vector_index["a"] # 0
print vector_index["b"] # 1

Monday, September 24, 2007

Python Load Time Is Slow

I'm very fond of CGI, the main reason is that if a CGI crashes - it's only this process for this user. Not the whole system.

However, Python is *slow* starting up - a problem in CGI world. I still use it but wish it'll load faster.

Here are some number for comparison (all programs just print "Hello there" and exit):

hw real: 0.001 user: 0.001 sys: 0.000
hwcc real: 0.002 user: 0.001 sys: 0.001
hw.lua real: 0.004 user: 0.001 sys: 0.004
hw.pl real: 0.004 user: 0.002 sys: 0.001
hw.rb real: 0.006 user: 0.004 sys: 0.002
hw.php real: 0.017 user: 0.013 sys: 0.005
hw.py real: 0.019 user: 0.011 sys: 0.008
hw.lsp real: 0.023 user: 0.011 sys: 0.011
hw.scm real: 0.027 user: 0.019 sys: 0.008
hwcs.exe real: 0.036 user: 0.029 sys: 0.007
HT.class real: 0.084 user: 0.027 sys: 0.01


See the makefile below for which is each program.
As you can see Python is somewhere in the middle, not as bad as Java and C#, but about 5 times slower than Perl.

Makefile:
SCRIPTS = hw.py hw.rb hw.pl hw.lsp hw.scm hw.lua hw.php
GENERATED = hw hwcc hwcs.exe
JAVA = HT.class
PROGRAMS = $(SCRIPTS) $(GENERATED) $(JAVA)

all: $(PROGRAMS) times
@echo DONE

hw: hw.c
gcc -o $@ -O3 $<

hwcc: hw.cc
g++ -o $@ -O3 $<

HT.class: hw.java
javac $<


and timeit is:

#!/bin/bash

TIMEFORMAT='real: %3R user: %3U sys: %3S'
SPACES=" "
MAXLEN=10


for program in $*;
do
name=${program/.class/}
if [ ${program/.exe/} != $program ]; then
timestr=`(time mono $program > /dev/null) 2>&1`
elif [ $name == $program ]; then
timestr=`(time ./$program > /dev/null) 2>&1`
else
timestr=`(time java -client $name > /dev/null) 2>&1`
fi
padlen=$(($MAXLEN - ${#program}))
echo "${program}${SPACES:0:$padlen}${timestr}"
done

Wednesday, August 29, 2007

Simple launcher for XFCE


I'm using xfce4 as a window manager, it has a nice launcher called xfrun4, however it only tries to execute applications.

I've written a little launcher that uses exo-open to open it's argument. This way I can open PDF files, directories etc.
(It's not as fancy as Mac's QuickSilver or Windows SlickRun, but it does the job)

In order to get quick access, open the keyboard settings, create a new theme (you can't change the default) and add the launcher there. I usually go with "CTRL-SHIFT-K" to activate.


#!/usr/bin/env python
'''Simple lanucher'''

from Tkinter import Tk, Label, Entry
from tkFont import Font
from tkMessageBox import showerror

from os.path import exists, expanduser
from os import environ, popen

def launch(name):
name = expanduser(name)
if not exists(name):
fullname = popen("which %s 2>/dev/null" % name).read().strip()
if not fullname:
raise ValueError("can't find %s" % name)
name = fullname

popen("/usr/bin/exo-open \"%s\"" % name).read()


USER_CANCEL = 0
ROOT = None
COMMAND = None

def quit(event):
global USER_CANCEL

USER_CANCEL = 1
ROOT.quit()

def build_ui():
global ROOT, COMMAND

ROOT = Tk()
ROOT.title("Launchie")
ROOT.bind("<Escape>", quit)
COMMAND = Entry(width=80, font=Font(size=14))
COMMAND.pack()
COMMAND.bind("<Return>", lambda e: ROOT.quit())

def show_ui():
global USER_CANCEL

USER_CANCEL = 0
COMMAND.focus()
ROOT.mainloop()

return COMMAND.get().strip()


def main(argv=None):
if argv is None:
import sys
argv = sys.argv

from optparse import OptionParser

parser = OptionParser("usage: %prog")

opts, args = parser.parse_args(argv[1:])
if len(args) != 0:
parser.error("wrong number of arguments") # Will exit


build_ui()

while 1:
try:
command = show_ui()
if USER_CANCEL:
raise SystemExit

if not command:
showerror("Launchie Error", "Please enter *something*")
continue

launch(command)
break
except ValueError:
showerror("Lanuchie Error", "Can't launch %s" % command)

if __name__ == "__main__":
main()


The reason I chose Tkinter is that it's already installed with Python and it's good enough for simple stuff like this.

Tuesday, August 21, 2007

start

Many times, I open files from the command line.
However each OS has it's own utility for opening file, so I have this little script called start (yes, I started my life on windows ;).

#!/bin/bash
# Open a file from command line, multi OS

# Miki Tebeka <miki.tebeka@gmail.com>

if [ $# -ne 1 ]; then
echo "usage: `basename $0` PATH"
exit 1
fi

if [ ! -e $1 ]; then
echo "error: can't find $1" 1>&2
exit 1
fi

case `uname` in
Linux) open=exo-open;;
Darwin) open=open;;
CYGWIN*) open=cygstart;;
MINGW32*) open=start;;
*) echo "error: no start program for `uname` platform" 1>&2; exit 1;;
esac

$open "$1"

Friday, August 10, 2007

Supporting Search Query Syntax

It's very easy to add support for search-engine like syntax in your program.
The idea is to convert the query to a Python expression and then evaluate it.

We'll support the following syntax:
word1 word2       - word1 and word2
word1 AND word2 - word1 and word2
word1 word2 - word1 and word2
word1 OR word2 - word1 ord word2
NOT word - Not containing word
The code is very simple:
def is_operator(token):
return token in set(["and", "not", "or", "(", ")"])

def should_insert_and(expr, token):
if not expr:
return 0

if is_operator(expr[-1]):
return 0

if is_operator(token):
return 0

return 1

def match(query, text):
words = set(text.lower().split())

expr = []
for token in query.lower().split():

if should_insert_and(expr, token):
expr.append("and")

if is_operator(token):
expr.append(token)
else:
expr.append(token in words)

py_expr = " ".join(map(str, expr))
return eval(py_expr)

def test():
assert match("a", "a"), "a --- a"
assert not match("a", ""), " --- a"
assert match("a AND b", "a c b"), "a c b --- a AND b"
assert not match("a AND b", "a c"), "a c --- a AND b"
assert match("NOT ( a OR b )", "z"), "z --- NOT ( a OR b )"
assert match("a OR b", "b"), "b --- a OR b"
Notes:
1. We don't do any fancy tokenization (text and query), but in most cases this should be enough.
2. We place an AND where it's missing.

Thursday, August 02, 2007

Cheetah Templates

Currently doing some web development and found Cheetah very useful.
I like Cheetah since it's syntax is very similar to Python and I can use my existing Python objects with it.

I have one master template that set the site general site look and feel (with the master CSS of course).
#from time import ctime

#attr NAME = "???"

#def head
#end def

#def body
OOOPS, head will roll...
#end def

<html>
<head>
<link rel="stylesheet" type="text/css" href="style.css" />
$head
</head>
<body>
<div class="header">My Wonderful Site - $NAME</div>
$body

<hr />
<div class="footer">
Generated $ctime()
</div>
</body>
</html>
$head and $body are place holders that the specific pages will fill.
Pages also define $NAME which will be shown in the header.

The an specific page (index.tmpl) can be:

#include "master.tmpl"

#attr NAME = "INDEX"

#def body
This is my site index page, see also <a href="other.cgi">other page</a>. <br />

Oh, and also random = $random;
#end def
And the CGI script:

#!/usr/local/bin/python

from Cheetah.Template import Template

from random import randint


def main():
random = randint(0, 100)

print "Content-Type: text/html"
print

page = Template(file="index.tmpl", searchList=[locals()])
print page.respond()

if __name__ == "__main__":
main()
Note that I pass locals() as the search list. This frees me from creating a mapping dictionary (exporting random to the template).

That's about it, you can use the master template and the site main CSS to have a uniform looking site and let each page implement just the $body and $head if it needs to.

Wednesday, July 18, 2007

Mini Excel


No so small as the calculator, but small enough (120 lines of code).
It can do any Python expression as a formula, support cell reference and ranges.

Monday, July 16, 2007

Watch that "yield"

Assume you have a program:
def f():
print "F"
yield 1

if __name__ == "__main__":
f()
and you run it, nothing is printed.
Then you comment out the "yield" statement, and F is printed out.

I actually went a filled a bug report. I need to know better than that :)

Raymond pointed out that in the first case, the yield statement causes the function to become a generator and nothing is being run until next is called.

This means Python is behaving as expected, however I'd wish for Python or Pychecker to have a GCC like statement with no effect warning.

Thursday, June 14, 2007

timeit

Sometimes speed is important. The timeit modules lets you find how fast you are.
from timeit import Timer

def fast_fib(n):
if n < 2:
return 1

a, b = 1, 1
for i in range(n - 1):
a, b = b, a + b

return b

def slow_fib(n):
if n < 2:
return 1

return slow_fib(n - 1) + slow_fib(n - 2)


INDEX = 20
TIMES = 100

fast_timer = Timer("fast_fib(INDEX)", "from __main__ import fast_fib, INDEX")
slow_timer = Timer("slow_fib(INDEX)", "from __main__ import slow_fib, INDEX")

print "slow:", slow_timer.timeit(TIMES) / TIMES
print "fast:", fast_timer.timeit(TIMES) / TIMES
On my machine this gives:

fast: 5.11884689331e-06
slow: 0.00996325016022
However sometimes you to send your function some more complex data, plus you don't want to add too much timing code into the top level of your module.
One way to do it is:
def benchmark():
benchmark.index = 20
timer = Timer("fast_fib(benchmark.index)",
"from __main__ import fast_fib, benchmark")
num_runs = 100

print timer.timeit(num_runs) / num_runs

def main(argv=None):
if argv is None:
import sys
argv = sys.argv

from optparse import OptionParser

parser = OptionParser("usage: %prog [options] MESSAGE")
parser.add_option("--benchmark", help="run benchmark",
dest="benchmark", action="store_true", default=0)

opts, args = parser.parse_args(argv[1:])

if opts.benchmark:
benchmark()
raise SystemExit()

if len(args) != 1:
parser.error("wrong number of arguments") # Will exit

# Do main program stuff here
try:
print fast_fib(int(args[0]))
except ValueError:
raise SystemExit("error: %s - bad number" % args[0])

if __name__ == "__main__":
main()

Wednesday, June 06, 2007

reStructuredText

I like to write documentation in a textual format. This way it's easy to view the changes in a regular diff tool and you can use almost any text editor to view the source.

The down side that you usually need to compile the documentation - no WYSIWYG.

I used to like LaTex. It produces excellent results out-of-the-box. And the math support is second to none.

However, reStructuedText has two advantages:
1. You can read the source directly and understand it
2. It produces good HTML (Yes, I know about latex2html)

You can also produces good PDF using rst2latex and then pdflatex.

A short document example:

===========
Hello World
===========
:Author: Miki Tebeka <miki@mikitebeka.com>
:Date: $Date: 2007-06-05 21:02:04 -0700 (Tue, 05 Jun 2007) $

.. contents::

Chapter 1
=========
In the beginning ...

Sub Chapter 1
-------------
There was LaTex_ [#]_

Chapter 2
=========
And then there was reST_

::
  
   That can have preformatted
   text


----

.. _LaTex: http://tug.org
.. _reST: http://docutils.sf.net/rst.html

.. [#] Which is still very good

.. comment: vim: ft=rst spell


The results using this makefile are:
%.html: %.txt
 rst2html.py --stylesheet style.css $< $@

%.pdf: %.tex
 pdflatex $<

%.tex: %.txt
 rst2latex.py $< $@

all: hw.html hw.pdf

clean:
 rm -f *.aux *.log *.pdf *.html *.out

fresh: clean all

.PHONY: all clean fresh



HTML


PDF


Final Notes


There are other such tools: markdown, asciidoc and others. I happen to like reST.

I use the following stylesheets (can't remember the URL I got them from):
style.css
/*
:Author: Fred L. Drake, Jr.
:date: $Date$
:version: $Revision$

This stylesheet combines some ideas from the two stylesheets
distributed with docutils and enhances them for Zope 3 documentation.
*/

@import url(default.css);

div.document {
  margin: 0px 1em 1em 4em;
  padding: 0px; }

div.document a {
  text-decoration: none; }

div.document a[href] {
  text-decoration: underline; }

div.document h1.title {
  background-image: url("zope3logo.gif");
  background-position: -6px -4px;
  background-repeat: no-repeat;
  font-size: 150%;
  min-height: 50px; }

div.document div.section {
  margin: 0px 0px 1.5em 0px; }

div.document div.section h1 {
  background-color: rgb(230,230,230);
  margin-left: -2em;
  padding: 0.2em;
  padding-left: 0.35em;
  padding-top: 0.35em;
  /* This grey underline make this more visually distinctive on LCD
     monitors, which often don't have enough contrast. */
  border-right: thin solid rgb(180,180,180);
  border-bottom: thin solid rgb(180,180,180); }

div.document div.section div.section div.section h3 {
  margin-bottom: -0.5em; }

div.document h1 {
  font-family: sans-serif;
  font-size: 135%; }

div.document h2 {
  font-family: sans-serif;
  font-size: 120%; }

div.document h3 {
  font-family: sans-serif;
  font-size: 105%; }

div.document h4 {
  font-family: sans-serif;
  font-size: 100%; }

div.document h5 {
  font-family: sans-serif;
  font-size: 100%; }

div.document h6 {
  font-family: sans-serif;
  font-style: italic;
  font-size: 100%; }

div.document hr {
  width: 75%; }

div.document .literal .pre {
  background-color: white;
  font-family: lucidatypewriter, "lucida typewriter", sans-serif; }

div.document .literal-block {
  border: thin solid rgb(180,180,180);
  font-family: lucidatypewriter, "lucida typewriter", monospace;
  font-size: 80%;
  padding: 0.5em; }

div.document table.table {
  margin-left: 2em;
  margin-right: 2em; }

div.document table.table thead {
  background-color: rgb(230,230,230); }

/* docutils uses the "option" class with both "col" and "span"
   elements, so we have to be explicit here */
div.document .option-list span.option {
  font-weight: bold; }

div.document .option-list kbd {
  font-family: inherit; }


default.css
/*
:Author: David Goodger
:Contact: goodger@users.sourceforge.net
:date: $Date$
:version: $Revision$
:copyright: This stylesheet has been placed in the public domain.

Default cascading style sheet for the HTML output of Docutils.
*/

div.document .first {
  margin-top: 0 }

div.document .last {
  margin-bottom: 0 }

div.document a.toc-backref {
  text-decoration: none ;
  color: black }

div.document dd {
  margin-bottom: 0.5em }

div.document div.abstract {
  margin: 2em 5em }

div.document div.abstract p.topic-title {
  font-weight: bold ;
  text-align: center }

div.document div.attention,
div.document div.caution,
div.document div.danger,
div.document div.error,
div.document div.hint,
div.document div.important,
div.document div.note,
div.document div.tip,
div.document div.warning,
div.document div.admonition {
  margin: 2em ;
  border: medium outset ;
  padding: 1em }

div.document div.attention p.admonition-title,
div.document div.caution p.admonition-title,
div.document div.danger p.admonition-title,
div.document div.error p.admonition-title,
div.document div.warning p.admonition-title {
  color: red ;
  font-weight: bold ;
  font-family: sans-serif }

div.document div.hint p.admonition-title,
div.document div.important p.admonition-title,
div.document div.note p.admonition-title,
div.document div.tip p.admonition-title,
div.document div.admonition p.admonition-title {
  font-weight: bold ;
  font-family: sans-serif }

div.document div.dedication {
  margin: 2em 5em ;
  text-align: center ;
  font-style: italic }

div.document div.dedication p.topic-title {
  font-weight: bold ;
  font-style: normal }

div.document div.figure {
  margin-left: 2em }

div.document div.footer,
div.document div.header {
  font-size: smaller }

div.document div.sidebar {
  margin-left: 1em ;
  border: medium outset ;
  padding: 0em 1em ;
  background-color: #ffffee ;
  width: 40% ;
  float: right ;
  clear: right }

div.document div.sidebar p.rubric {
  font-family: sans-serif ;
  font-size: medium }

div.document div.system-messages {
  margin: 5em }

div.document div.system-messages h1 {
  color: red }

div.document div.system-message {
  border: medium outset ;
  padding: 1em }

div.document div.system-message p.system-message-title {
  color: red ;
  font-weight: bold }

div.document div.topic {
  margin: 2em }

div.document h1.title {
  text-align: center }

div.document h2.subtitle {
  text-align: center }

div.document hr {
  width: 75% }

div.document ol.simple, ul.simple {
  margin-bottom: 1em }

div.document ol.arabic {
  list-style: decimal }

div.document ol.loweralpha {
  list-style: lower-alpha }

div.document ol.upperalpha {
  list-style: upper-alpha }

div.document ol.lowerroman {
  list-style: lower-roman }

div.document ol.upperroman {
  list-style: upper-roman }

div.document p.attribution {
  text-align: right ;
  margin-left: 50% }

div.document p.caption {
  font-style: italic }

div.document p.credits {
  font-style: italic ;
  font-size: smaller }

div.document p.label {
  white-space: nowrap }

div.document p.rubric {
  font-weight: bold ;
  font-size: larger ;
  color: darkred ;
  text-align: center }

div.document p.sidebar-title {
  font-family: sans-serif ;
  font-weight: bold ;
  font-size: larger }

div.document p.sidebar-subtitle {
  font-family: sans-serif ;
  font-weight: bold }

div.document p.topic-title {
  font-weight: bold }

div.document pre.address {
  margin-bottom: 0 ;
  margin-top: 0 ;
  font-family: serif ;
  font-size: 100% }

div.document pre.line-block {
  font-family: serif ;
  font-size: 100% }

div.document pre.literal-block, pre.doctest-block {
  margin-left: 2em ;
  margin-right: 2em ;
  background-color: #eeeeee }

div.document span.classifier {
  font-family: sans-serif ;
  font-style: oblique }

div.document span.classifier-delimiter {
  font-family: sans-serif ;
  font-weight: bold }

div.document span.interpreted {
  font-family: sans-serif }

div.document span.option {
  white-space: nowrap }

div.document span.option-argument {
  font-style: italic }

div.document span.pre {
  white-space: pre }

div.document span.problematic {
  color: red }

div.document table {
  margin-top: 0.5em ;
  margin-bottom: 0.5em }

div.document table.citation {
  border-left: solid thin gray ;
  padding-left: 0.5ex }

div.document table.docinfo {
  margin: 2em 4em }

div.document table.footnote {
  border-left: solid thin black ;
  padding-left: 0.5ex }

div.document td,
div.document th {
  padding-left: 0.5em ;
  padding-right: 0.5em ;
  vertical-align: top }

div.document th.docinfo-name,
div.document th.field-name {
  font-weight: bold ;
  text-align: left ;
  white-space: nowrap }

div.document h1 tt,
div.document h2 tt,
div.document h3 tt,
div.document h4 tt,
div.document h5 tt,
div.document h6 tt {
  font-size: 100% }

div.document tt {
  background-color: #eeeeee }

div.document ul.auto-toc {
  list-style-type: none }

Thursday, May 17, 2007

Websession

A nice class for supporting sessions in CGI scripts.
Usage Example:

Monday, May 07, 2007

Avoiding Indent

To reduce the amount of indentation, you can negate your logic:

def positive_logic(x):
if x > 2:
y = f(x)
if y < 10:
g = f(y)
if g > 0:
do_cool_stuff(g)

will become:

def negative_logic(x):
if x <= 2:
return
y = f(x)
if y >= 10:
return
g = f(y)
if g <= 0:
return
do_cool_stuff(g)

Tuesday, April 24, 2007

Auto building C extension

Not as good as Perl's inline module, however this little tricks will build the C extension the 1'st time the module is loaded. (Works on Linux, probably on Mac and Windows with development tools installed)

Let's call our module autobuild, the in the autobuild directory we'll have:

__init__.py

def _build():
from os.path import getmtime, isfile, dirname, join
from sys import executable
from os import system

from setup import DYNLIB, SRC_FILE

MODULE_DIR = dirname(__file__)

def _run(cmd):
return system("(cd \"%s\" && %s) > /dev/null 2>&1" % (MODULE_DIR, cmd))

_full_src = join(MODULE_DIR, SRC_FILE)
_full_dynlib = join(MODULE_DIR, DYNLIB)

if (not isfile(_full_dynlib)) or (getmtime(_full_dynlib) < getmtime(_full_src)):
assert _run("%s setup.py build_ext -i" % executable) == 0, "build error"

_build()
del _build
from _greet import *

setup.py


from distutils.core import Extension, setup

MODULE_NAME = "_greet"
DYNLIB = MODULE_NAME + ".so"
SRC_FILE = MODULE_NAME + ".c"

if __name__ == "__main__":
setup(ext_modules=[Extension(MODULE_NAME, [SRC_FILE])])

_greet.c

#include <python.h>
#include <stdio.h>

static PyObject *
greet_greet(PyObject *self, PyObject *args)
{
char *name;

if (!PyArg_ParseTuple(args, "s", &name)) {
return NULL;
}

printf("Hello %s\n", name);

return Py_BuildValue("");
}

static PyMethodDef GreetMethods[] = {
{ "greet", greet_greet, METH_VARARGS,
"Print a friendly greeting."
},
{NULL, NULL, 0, NULL} /* Sentinel */
};

PyMODINIT_FUNC
init_greet(void)
{
Py_InitModule("_greet", GreetMethods);
}

Friday, April 13, 2007

Using Multi-Line String for Regular Expressions

Python (like C), concatenates strings that are separated only by white space.
This helps writing clearer regular expressions:

#!/usr/bin/env python
import re

# 2007-04-01 11:20
find_time = re.compile(
   "(?P<year>\d{4})"  # 4 digit year
   "-"
   "(?P<month>\d{2})"  # 2 digit month
   "-"
   "(?P<day>\d{2})"  # 2 digit day
   "\s+"        # white space(s)
   "(?P<hour>\d{2})"  # 2 digit hour
   ":"
   "(?P<minute>\d{2})"  # 2 digit minute
   ).search

match = find_time("The exact time is 2007-04-01  11:20.")
assert match, "can't find time"
print "MONTH: %s" % match.group("month")

Friday, March 30, 2007

HTML Entities

Quick way to see how are all HTML entities are displayed in your browser:


from urllib import urlopen
import re
import webbrowser

W3_URL = "http://www.w3.org/TR/WD-html40-970708/sgml/entities.html"
FILE_NAME = "/tmp/html-entities.html"
find_entity = re.compile("!ENTITY\s+([A-Za-z][A-Za-z0-9]+)").search

fo = open(FILE_NAME, "wt")

print >> fo, "<html><body><table border=\"1\">"

for line in urlopen(W3_URL):
match = find_entity(line)
if match:
entity = match.groups()[0]
print >> fo, "<tr><td>%s</td><td>&%s;</td></tr>" % (entity, entity)
print >> fo, "</table></body></html>"
fo.close()

webbrowser.open(FILE_NAME)

Say "NO" to Internet Violence

I'll make an exception for Kathy Sierra, and post a non-technical entry.

Just say "NO" to any violence in the internet, make it a better place for all of us.

Kathy, I hope you'll find the strength to overcome this.

Tuesday, March 27, 2007

Pushing Data - The Easy Way

One of the fastest ways to implement "pushing data to a server" is to have a CGI script on the server and push data to it from the clients.

This way you don't need to write a server, design a protocol, ... Just use an existing HTTP server (such as lighttpd) with CGI.

CGI Script:
#!/usr/bin/env python

from cgi import FieldStorage
from myapp import do_something_with_data

ERROR = "<html><body>Error: %s</body></html>"

def main():
print "Content-Type: text/html"
print

form = FieldStorage()
data = form.getvalue("data", "")
key = form.getvalue("key", "").strip()
if not (key and data):
raise SystemExit(ERROR % "NO 'key' or 'data'")

try:
do_something_with_data(key, data)
except Exception, e:
raise SystemExit(ERROR % e)

print "<html><body>OK</body></html>"

if __name__ == "__main__":
main()

"Pushing" script:
#!/usr/bin/env python

from urllib import urlopen, urlencode

CGI_URL = "http://localhost:8080/load.cgi"
def push_data(key, data):
query = urlencode([("data", data), ("key", key)])
try:
urlopen(CGI_URL, query).read()
except IOError, e:
pass # FIXME: Handle error

def main(argv=None):
if argv is None:
import sys
argv = sys.argv

from optparse import OptionParser
from os.path import isfile, basename

parser = OptionParser("usage: %prog FILENAME")

opts, args = parser.parse_args(argv[1:])
if len(args) != 1:
parser.error("wrong number of arguments") # Will exit

filename = args[0]
if not isfile(filename):
raise SystemExit("error: can't find %s" % filename)

key = basename(filename)
data = open(filename, "rb").read()

push_data(key, data)


if __name__ == "__main__":
main()



(Thanks to Martin for the idea)

Wednesday, March 21, 2007

defaultdict

Python 2.5 has a defaultdict dictionary in the collections
module.
defaultdict takes a factory function in the constructor. This function
will create the default value each time you try to get a missing item.

Then you can write a word histogram function like this:
from collections import defaultdict
def histogram(text):
histogram = defaultdict(int) # int() -> 0
for word in text.split():
histogram[word] += 1
return histogram
Or, if you want to store the location of the words as well
def histogram(text):
histogram = defaultdict(list) # list() -> []
for location, word in enumerate(text.split()):
histogram[word].append(location)
return histogram

Wednesday, February 21, 2007

AJAX 101


MochiKit is one of many AJAX toolkits out
there. I found it very intuetive and fun to use.

We'll construct a minimal AJAX application using MochiKit, the application will
pull two values A and B from the server and update them on a
web page. (See the buttom for a list of packages/utilities used).

The web server will be a simple CGI (get_values.cgi) script that
returns a JSON hash table with the desired values:

get_values.cgi

#!/usr/bin/env python

import simplejson
from random import randint

print "Content-Type: text/plain"
print

low, high = 0, 100

data = {
"A" : randint(low, high),
"B" : randint(low, high),
}

print simplejson.dumps(data)
Our HTML page is very simple, note that:
  • We give an id for each table cell we want to change
  • We load MochiKit
  • After that we load our script

index.html

<html>
<head>
<title>pythonwise - MochiKit Demo
<!-- Load MochiKit -->
<script type="text/javascript" src="/MochiKit/MochiKit.js">
<!-- Load our script -->
<script type="text/javascript" src="/values.js">
</title>
<!-- Have some style -->
<style>
table {
background-color: lightskyblue;
border-style: solid;
border-width: 5px;
width: 20%;
text-align: center;
}
td {
text-align: center;
font-family: Courier, monospace;
font-size: 40px;
}
</style>

</head>
<body>
<center>
<h1>pythonwise - MochiKit Demo
<div class="content">
<!-- Just a simple table with the values we want to show -->
<table>
<tr>
<td>A
<td id="A">???
</tr>
<tr>
<td>B
<td id="B">???
</tr>
</table>
</div>
<hr width="20%" />
A MochiKit demo from
<a href="http://pythonwise.blogspot.com">pythonwise, by
<a href="mailto:miki.tebeka@gmail.com">Miki
</center>
</body>
</html>
What's left is our little script:

values.js

function connection_error () {
alert("Connection Error!");
}

function process_values(data) {
/* Even JavaScript has some introspection */
for (key in data) {
var new_value = data[key];
var color = "black"; /* No chage color */
var element = getElement(key);
var last_value = parseInt(element.innerHTML);

if (last_value == NaN) { /* First time */
color = "black";
}
else if (new_value > last_value) {
color = "green";
}
else if (new_value < last_value) {
color = "red";
}

/* Change to new value */
element.innerHTML = new_value;
element.normalize()
element.style["color"] = color;
}

/* Wait 3 seconds and refresh again */
callLater(3, get_updates);
}

function get_updates() {
var data = loadJSONDoc("get_values.cgi");
data.addCallbacks(process_values, connection_error);
}

/* Call get_updates when window is loaded */
connect(window, "onload", get_updates);

What we get is something that looks like the image at the head of this article.

If you want to run this demo, you'll need a web server for the CGI.

I'm using lighttpd because it's simple and
fast. Here is the configuration file for the demo:

lighttpd.conf

# lighhtpd configuration file, see http://trac.lighttpd.net/trac/wiki/Docs for
# more information

server.modules = (
"mod_access",
"mod_cgi",
)

server.document-root = "/home/mtebeka/mochikit-demo"
server.port = 8080

# .html is HTML
mimetype.assign = ( ".html" => "text/html" )
# Look for index.html
index-file.names = ( "index.html" )

# .cgi are not static
static-file.exclude-extensions = ( ".cgi" )

# Use Python to run CGI scripts
cgi.assign = ( ".cgi" => "/usr/local/bin/python" )

Run with /usr/sbin/lighttpd -f lighttpd.conf.


That's it, I hope that next time you'll consider AJAX - it's not that hard :)

Resources

Friday, January 26, 2007

Access SQL Query Results By Column Name

If work with sqlalchemy, you can access columns by their name and not just by their position (e.g. row.id instead of row[0]).

If you can't use sqlalchemy, you can still access columns by their names, at least on SQLite and PostgreSQL.

Wednesday, January 24, 2007

partial

Python 2.5 introduced the functools module and in it partial.

partial allow you to define a partial (doh!) application of a function to arguments. My common use (currently) is for re.sub
>>> from functools import partial
>>> import re
>>> remove_prefix = partial(re.compile("prefix: ").sub, "")
>>> remove_prefix("prefix: hello")
'hello'
>>> remove_prefix("hello")
'hello'
>>>

Wednesday, January 03, 2007

MochiKit and FireBug

Happy New Year!

Just a quick one ...

Doing a lot of AJAX lately. Found out that MochiKit and FireBug (there is even FireBug lite now) are excellent development tools. I made some very cool stuff with minimal learning curve.

More on this later.

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