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nukl nukl - 1 year ago 79
Python Question

Find all occurrences of a substring in Python

Python has

to get the index of a substring in string.

I wonder, maybe there is something like
which can return all founded indexes (not only first from beginning or first from end)?

For example:

string = "test test test test"

print string.find('test') # 0
print string.rfind('test') # 15

#that's the goal
print string.find_all('test') # [0,5,10,15]


There is no simple built-in string function that does what you're looking for, but you could use the more powerful regular expressions:

>>> [m.start() for m in re.finditer('test', 'test test test test')]
[0, 5, 10, 15]

If you want to find overlapping matches, lookahead will do that:

>>> [m.start() for m in re.finditer('(?=tt)', 'ttt')]
[0, 1]

If you want a reverse find-all without overlaps, you can combine positive and negative lookahead into an expression like this:

>>> search = 'tt'
>>> [m.start() for m in re.finditer('(?=%s)(?!.{1,%d}%s)' % (search, len(search)-1, search), 'ttt')]

re.finditer returns a generator, so you could change the [] in the above to () to get a generator instead of a list which will be more efficient if you're only iterating through the results once.