Getting indices of True values in a boolean list
list, python
Solution
Use `enumerate`, `list.index` returns the index of first match found.
>>> t = [False, False, False, False, True, True, False, True, False, False, False, False, False, False, False, False]
>>> [i for i, x in enumerate(t) if x]
[4, 5, 7]
For huge lists, it'd be better to use `itertools.compress`:
>>> from itertools import compress
>>> list(compress(xrange(len(t)), t))
[4, 5, 7]
>>> t = t*1000
>>> %timeit [i for i, x in enumerate(t) if x]
100 loops, best of 3: 2.55 ms per loop
>>> %timeit list(compress(xrange(len(t)), t))
1000 loops, best of 3: 696 µs per loop
Problem
I have a piece of my code where I'm supposed to create a switchboard. I want to return a list of all the switches that are on. Here "on" will equal `True` and "off" equal `False`. So now I just want to return a list of all the `True` values and their position. This is all I have but it only return the position of the first occurrence of `True` (this is just a portion of my code): ``` self.states = [False, False, False, False, True, True, False, True, False, False, False, False, False, False, False, False] def which_switch(self): x = [self.states.index(i) for i in self.states if i == True] ``` This only returns "4"