Fastest way to calculate leading whitespace

[Daniel Skinner]

That solution actually runs slower then the generator method.

On Sat, May 8, 2010 at 12:33 PM, Shashank Singh <
shashank.sunny.singh at gmail.com> wrote:

>
>
> On Sat, May 8, 2010 at 10:49 PM, dasacc22 <dasacc22 at gmail.com> wrote:
>
>> Hi
>>
>> This is a simple question. I'm looking for the fastest way to
>> calculate the leading whitespace (as a string, ie '    ').
>>
>> Here are some different methods I have tried so far
>> --- solution 1
>>
>> a = '    some content\n'
>> b = a.strip()
>> c = ' '*(len(a)-len(b))
>>
>
> use lstrip if you want to remove leading whitespaces only.
> strip removes trailing white spaces too
>
>>
>> --- solution 2
>>
>> a = '    some content\n'
>> b = a.strip()
>> c = a.partition(b[0])[0]
>>
>> --- solution 3
>>
>> def get_leading_whitespace(s):
>>    def _get():
>>        for x in s:
>>            if x != ' ':
>>                break
>>            yield x
>>    return ''.join(_get())
>>
>
> why do you need a generator (and as you mentioned the extra function call
> overheads)?
>
> How about this?
>
> def get_leading_whitespaces(s):
>     count = 0
>     for c in s:
>         if c != ' ': break
>         count += 1
>     return ' ' * count
>
>
>>
>> ---
>>
>> Solution 1 seems to be about as fast as solution 2 except in certain
>> circumstances where the value of b has already been determined for
>> other purposes. Solution 3 is slower due to the function overhead.
>>
>> Curious to see what other types of solutions people might have.
>>
>> Thanks,
>> Daniel
>> --
>> http://mail.python.org/mailman/listinfo/python-list
>>
>
>
>
> --
> Regards
> Shashank Singh
> Senior Undergraduate, Department of Computer Science and Engineering
> Indian Institute of Technology Bombay
> shashank.sunny.singh at gmail.com
> http://www.cse.iitb.ac.in/~shashanksingh
>
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