Regular expressions and Python

[ENBeginner]

Hello,

I am working with Regular Expressions in Python.

I have a text file (authors.txt) file that contains the first and last name of an author separated with a whitespace, then a whitespace and the book title:

Peter Smith The Lobster story
Christine Bower In the closet
Tom Martin How to paint your furniture


My questions:

1) I want to transform the name into a string like this:

Peter Smith => psmith

I tried to get the first character of the first group, then to concatenate it with the second group and transform the whole string into lower case.


2.) Then I want to transform the book title into a string like this:

The Lobster story => the_lobster_story

I guess I just have to replace the whitespaces with an underscore '_' and transform the whole thing into lowercase but I don't know what function to use and how...


Then I wrote this script.py:


import re
import string

rgx = re.compile("(([A-Z])+\w+)[ ](([A-Z])+\w+)[ ]([^:]+)")

inf = open('authors.txt', 'r')
outf= open('authors2.txt', 'w')


for row in inf.readlines():
corr = rgx.search(row)
#these variables are false
first_name = corr.group(0)
last_name = corr.group(1)
name = corr.lower(first_name[0])+corr.lower(last_name)
title = corr.group(2)
title2 = title.lower(title.replace(' ', '_'))

if corr != None:
str = name ,"@bookstore.com" + " " + http://www.bookstore.org/", title2
outf.write(str)


inf.close()
outf.close()


Can anyone help?

[bvdet]

Please use code tags when posting code. Posting Guidelines - How to ask a question
You do not need regular expressions for this. Create an empty list to hold the results. Split the string, append the processed results to the list.

f = open('file_name')
output = []
for line in f:
    lineList = line.split()
    output.append(['%s%s' % (lineList[0][0].lower(), lineList[1].lower()), \
                   '_'.join([word.lower() for word in lineList[2:]])])
 
f.close()    
 
for item in output:
    print item
 

>>> ['psmith', 'the_lobster_story']
['cbower', 'in_the_closet']
['tmartin', 'how_to_paint_your_furniture']
>>>

[bvdet]

I modified your regex pattern somewhat and added names to the groups. Using names, it is easier to read the structure of the pattern, and you can access the matched substrings with the MatchObject.groupdict() method. The rest is almost the same code as the non-regex solution.

import re
 
rgx = re.compile(r'%s %s %s' % ('(?P<first_name>(?P<first_initial>[A-Z])?\w+)', \
                                '(?P<last_name>(?P<last_initial>[A-Z])?\w+)', \
                                '(?P<book_title>.+)'))
f = open(fn)
output = []
for line in f:
    m = rgx.search(line)
    dd = m.groupdict()
    output.append(['%s%s' % (dd['first_initial'].lower(), dd['last_name'].lower()), \
                   '_'.join([word.lower() for word in dd['book_title'].split()])])
 
f.close()    
 
for item in output:
    print item 

>>> ['psmith', 'the_lobster_story']
['cbower', 'in_the_closet']
['tmartin', 'how_to_paint_your_furniture']
>>>