[Tutor] print out lines that start with a word

[Liam Clarke]

H Ron, 

>>> import re
>>> f = open('c:/lines.txt').readlines()
>>> for line in f:
       match = re.search('^This',f)
       if line == match:
               print match

Hi Ron, 

Welcome to the wonderful world of Python.

from re.search.__doc__ ;

"Scan through string looking for a match to the pattern, returning
    a match object, or None if no match was found."


OK, so if there's a match, you get an object returned, otherwise it
returns None. So, you can boolean test this. I'm guessing you want to
print lines that start with this.

import re
f = file('c:/lines.txt) #Also, you can iterate over a file

for line in f:
   match = re.search('^This', line) #you want to search line by line? 
   if match:
      print line
   else:
      print "No match"


Or, you could store all the lines in a list to use afterwards - 

lineStore =[]
for line in f:
   match = re.search('^This', line) #you want to search line by line? 
   if match:
      lineStore.append(line)
   else:
      print "No match"

On Tue, 8 Feb 2005 21:36:55 -0800 (PST), Ron Nixon <nixonron at yahoo.com> wrote:
> Can anyone tell me what I've done wrong in this
> script.
> 
> I'm trying to get only the lines that start with
> "This" for a text file.
> 
> Here's what I wrote:
> 
> >>> import re
> >>> f = open('c:/lines.txt').readlines()
> >>> for line in f:
>         match = re.search('^This',f)
>         if line == match:
>                 print match
> 
> here's the error message I got:
> 
> Traceback (most recent call last):
>   File "<pyshell#34>", line 2, in -toplevel-
>     match = re.search('^This',f)
>   File "C:\Python24\lib\sre.py", line 134, in search
>     return _compile(pattern, flags).search(string)
> TypeError: expected string or buffer
> 
> Thanks in advance
> 
> 
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