CODEWITHSUNDEEP
pythonstringwindowpositionrange
O.rka
O.rka

Reputation: 30717

Find start and end positions of all occurrences within a string in Python

If you have a sequence:

example='abcdefabcdefabcdefg'

and your searching for:

searching_for='abc'

what function would give you a list with all the positions?

positions=[(0,2),(6-8),(12-14)]

i created a window list that splits 'example' by 3 so it goes from 'abc','bcd','cde'

windows=['abc', 'bcd', 'cde', 'def', 'efa', 'fab', 'abc', 'bcd', 'cde', 'def', 'efa', 'fab', 'abc', 'bcd', 'cde', 'def']

and used a for loop

for i in windows:
    if i == 'abc':

thats where i get stuck . . .

Upvotes: 8

Views: 16043

Answers (3)

miku
miku

Reputation: 188124

You can use regular expressions; the match objects come with position information attached. Example using Python 2:

>>> import re
>>> example = 'abcdefabcdefabcdefg'
>>> for match in re.finditer('abc', example):
        print(match.start(), match.end())
0 3
6 9 
12 15

Upvotes: 13

Thomas
Thomas

Reputation: 182000

This is elegantly expressed by a list comprehension:

positions = [(i, i + len(searching_for) - 1)
             for i in xrange(len(example))
             if example[i:].startswith(searching_for)]

Note that it's often more useful to have the end index point after the last character, rather than to the last character as you asked for (and the above code provides).

Upvotes: 3

user97370
user97370

Reputation:

The re module provides what you need.

import re
print [(m.start(0), m.end(0)) for m in re.finditer('abc', 'abcdefabcdefabcdefg')]

Upvotes: 4

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