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Should I use Python 2 or Python 3?

February 4, 2011 Leave a comment

Should I use Python 2 or Python 3?

This is a very common question when someone wants to learn Python. Here is a nice article about this topic: http://wiki.python.org/moin/Python2orPython3.

(Thanks Jaume for the link.)

Update (20110404)

If you are ready to dive in Python 3, here are some tutorials:

  • The official Python 3 tutorial (HTML, PDF)
  • Further Python 3 docs (c-api.pdf, distutils.pdf, documenting.pdf, extending.pdf, faq.pdf, howto-advocacy.pdf, howto-cporting.pdf, howto-curses.pdf, howto-descriptor.pdf, howto-doanddont.pdf, howto-functional.pdf, howto-logging-cookbook.pdf, howto-logging.pdf, howto-pyporting.pdf, howto-regex.pdf, howto-sockets.pdf, howto-sorting.pdf, howto-unicode.pdf, howto-urllib2.pdf, howto-webservers.pdf, install.pdf, library.pdf, reference.pdf, tutorial.pdf, using.pdf, whatsnew.pdf)
  • Dive Into Python 3 (HTML and PDF)

Update (20110526)

I follow the following simple guideline: I use that version of Python that comes with Ubuntu by default. In Ubuntu 10.10 it was Python 2.6, in Ubuntu 11.04 it’s Python 2.7. When they switch to Python 3.x, I will switch too.

Where does a page redirect to?

December 21, 2010 Leave a comment

Question

We have a page that redirects to another page. How to figure out where the redirection points to?

Answer

import urllib

s = "https://pythonadventures.wordpress.com?random"    # returns a random post
page = urllib.urlopen(s)
print page.geturl()    # e.g. http:// pythonadventures.wordpress.com/2010/10/08/python-challenge-1/

Credits

I found it in this thread.

Update (20121202)

With requests:

>>> import requests
>>> r = requests.get('https://pythonadventures.wordpress.com?random')
>>> r.url
u'https://pythonadventures.wordpress.com/2010/09/30/create-import-module/'
Categories: python Tags: , ,

unicode to ascii

December 17, 2010 Leave a comment

Problem

I had the following unicode string: “Kellemes Ünnepeket!” that I wanted to simplify to this: “Kellemes Unnepeket!”, that is strip “Ü” to “U”. Furthermore, most of the strings were normal ascii, only some of them were in unicode.

Solution

import unicodedata

title = ...   # get the string somehow
try:
    # if the title is a unicode string, normalize it
    title = unicodedata.normalize('NFKD', title).encode('ascii','ignore')
except TypeError:
    # if it was not a unicode string => OK, do nothing
    pass

Credits

I used the following resources:

Categories: python Tags: , , ,

Using MySQL from Python

December 14, 2010 Leave a comment

Problem

You want to interact with a MySQL database from your Python script.

Solution

First of all, you need to install the following package:

sudo apt-get install python-mysqldb

Then try the following basic script to check if everything is OK:

#!/usr/bin/env python

import MySQLdb

conn = MySQLdb.connect (host = "localhost",
                        user = "testuser",
                        passwd = "testpass",
                        db = "test")
cursor = conn.cursor ()
cursor.execute ("SELECT VERSION()")
row = cursor.fetchone ()
print "server version: ", row[0]
cursor.close ()
conn.close ()

Example:

We have a .csv file with two columns: symbol and name. Iterate through the lines and insert each line in a database table as a record.

#!/usr/bin/env python

import MySQLdb

f1 = open('./NYSE.csv',  'r')
# A line looks like this:
# ZLC;    Zale Corporation

conn = MySQLdb.connect(host = "localhost",
                       user = "user",
                       passwd = "passwd",
                       db = "table")
cursor = conn.cursor()

for line in f1:
    pieces = map(str.strip, line.split(';'))
    #print "'%s' => '%s'" % (pieces[0], pieces[1])
    query = "INSERT INTO symbol_name (symbol, name) VALUES (\"%s\", \"%s\")" % (pieces[0], pieces[1])
    #print query
    cursor.execute(query)

f1.close()

conn.commit()
cursor.close ()
conn.close ()

Links

There are lots of Python-MySQL tutorials on the net. Let’s see some of them:

Categories: python Tags:

Rename multiple files

November 2, 2010 Leave a comment

Problem

I scanned in 66 pages that are numbered from 11 to 76. However, the scanning software saved the files under the names Scan10032.JPG, Scan10033.JPG, …, Scan10097.JPG. I want to rename them to reflect the real numbering of the pages, i.e. 11.jpg, 12.jpg, …, 76.jpg.

Solution

#!/usr/bin/env python

import glob
import re
import os

files = glob.glob('*.JPG')  # get *.JPG in a list (not sorted!)
files.sort()                # sort the list _in place_
cnt = 11                    # start new names with 11.jpg

for f in files:
    original = f                                    # save the original file name
    result = re.search(r'Scan(\d+)\.JPG', f)        # pattern to match
    if result:                                      # Is there a match?
        new_name = str(cnt) + '.jpg'                # create the new name
        print "%s => %s" % (original, new_name)     # verify if it's OK
        # os.rename(original, new_name)             # then uncomment to rename
        cnt += 1                                    # increment the counter

Comments are inside the source code.

If you need a simpler rename (like removing a part of the file names), you can also use the rename command. In this post I give an example for that.

Categories: python Tags: , , , ,

Fluffy is gone

October 29, 2010 Leave a comment

We are sad to inform you that Fluffy, the world’s longest snake living in captivity, has died. 18-years-old and weighing 300-pounds Fluffy held the title of longest snake by Guinness World Records and was a hit attraction at Columbus Zoo.

Find more info here.

Categories: python Tags: ,
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