Parsing Strings

If you’re working with text files you’ll probably want to extract some specific substring which is implemented in strings. For example you want to split and collect the first and second half of e-mail address. First half of e-mail address is before the @ sign and second half is after the @ sign. Let’s look at the sentence:

From stephen.marquard@ uct.ac.za Sat Jan 5 09:14:16 2008

To pull out email by using the find method and string slicing. First, we will find the position of the @ sign. And then we will use string slicing to extract the portion of the string which we are looking for.

data = 'From stephen.marquard@uct.ac.za Sat Jan 5 09:14:16 2008'
atpos = data.find('@')
print atpos
sppos1 = data.find(' ')
print sppos1
sppos2 = data.find(' ', atpos)
print sppos2
host1 = data[sppos1+1:atpos]
host2 = data[atpos+1:sppos2]
print host1
print host2

Output

<21
4
31
stephen.marquard
uct.ac.za

We use a version of the find method which allows us to specify a position in the string where we want find to start looking.