How to find all occurrences of a substring?
There is no simple built-in string function that does what you're looking for, but you could use the more powerful regular expressions:
import re[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')]#[1]
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.
>>> help(str.find)Help on method_descriptor:find(...) S.find(sub [,start [,end]]) -> int
Thus, we can build it ourselves:
def find_all(a_str, sub): start = 0 while True: start = a_str.find(sub, start) if start == -1: return yield start start += len(sub) # use start += 1 to find overlapping matcheslist(find_all('spam spam spam spam', 'spam')) # [0, 5, 10, 15]
No temporary strings or regexes required.