re.search much slower then grep on some regular expressions

[Bruno Desthuilliers]

Bruno Desthuilliers a écrit :
> Henning_Thornblad a écrit :
>> What can be the cause of the large difference between re.search and
>> grep?
>>
>> This script takes about 5 min to run on my computer:
>> #!/usr/bin/env python
>> import re
>>
>> row=""
>> for a in range(156000):
>>     row+="a"
>> print re.search('[^ "=]*/',row)
>>
>>
>> While doing a simple grep:
>> grep '[^ "=]*/' input                  (input contains 156.000 a in
>> one row)
>> doesn't even take a second.
>>
>> Is this a bug in python?
> 
> Please re-read carefully your python code. Don't you think there's a 
> subtle difference between reading a file and buildin 156000 string 
> objects ?
> 

Mmm... This set aside, after testing it (building the string in a 
somewhat more efficient way), the call to re.search effectively takes 
ages to return. Please forget my previous post.