Stripping a string and getting start index and end index

Question

Is there any straightforward way in Python to strip a string and get the start index and the end index?

Example: Given the string ' hello world! ', I want to the stripped string 'hello world!' As well as the start index 2 and the and index 14.

' hello world! '.strip() only returns the stripped string.

I could write a function:

def strip(str):
    '''
    Take a string as input.
    Return the stripped string as well as the start index and end index.
    Example: '  hello world!   '  --> ('hello world!', 2, 14)
    The function isn't computationally efficient as it does more than one pass on the string.
    '''
    str_stripped = str.strip()
    index_start = str.find(str_stripped)
    index_end = index_start + len(str_stripped)
    return str_stripped, index_start, index_end

def main():
    str = '  hello world!   '
    str_stripped, index_start, index_end = strip(str)
    print('index_start: {0}\tindex_end: {1}'.format(index_start, index_end))

if __name__ == "__main__":
    main()

but I wonder whether Python or one popular library provides any built-in way to do so.

Answer 1

One option (probably not the most straight-forward) would be to do it with regular expressions:

>>> import re
>>> s = '  hello world!   '
>>> match = re.search(r"^\s*(\S.*?)\s*$", s)
>>> match.group(1), match.start(1), match.end(1)
('hello world!', 2, 14)

where in ^\s*(\S.*?)\s*$ pattern:

• ^ is a beginning of a string
• \s* zero or more space characters
• (\S.*?) is a capturing group that would capture a non-space character followed by any characters any number of times in a non-greedy fashion
• $ is an end of a string