[Tutor] Regular Expression Misunderstanding

[Kent Johnson]

Steve Nelson wrote:
> On 7/14/06, John Fouhy <john at fouhy.net> wrote:
>
>   
>>>>> m = re.match(...)
>>>>> dir(m)
>>>>>           
>> It will tell you what attributes the match object has.
>>     
>
> Useful - thank you.
>
> I am now confuse on this:
>
> I have a file full of lines beginning with the letter "b".  I want a
> RE that will return the whole line if it begins with b.
>
> I find if I do eg:
>
>   
>>>> m = re.search("^b", "b spam spam spam")
>>>> m.group()
>>>>         
> 'b'
>
> How do I get it to return the whole line if it begins with a b?
Use the match object in a test. If the search fails it will return None 
which tests false:

for line in lines:
  m = re.search(...)
  if m:
    # do something with line that matches

But for this particular application you might as well use 
line.startswith('b') instead of a regex.

Kent