Counting the number of True Booleans in a Python List

Question

I have a list of Booleans:

[True, True, False, False, False, True]

and I am looking for a way to count the number of True in t

Answer 1

Just for completeness' sake (sum is usually preferable), I wanted to mention that we can also use filter to get the truthy values. In the usual case, filter accepts a function as the first argument, but if you pass it None, it will filter for all "truthy" values. This feature is somewhat surprising, but is well documented and works in both Python 2 and 3.

The difference between the versions, is that in Python 2 filter returns a list, so we can use len:

>>> bool_list = [True, True, False, False, False, True]
>>> filter(None, bool_list)
[True, True, True]
>>> len(filter(None, bool_list))
3

But in Python 3, filter returns an iterator, so we can't use len, and if we want to avoid using sum (for any reason) we need to resort to converting the iterator to a list (which makes this much less pretty):

>>> bool_list = [True, True, False, False, False, True]
>>> filter(None, bool_list)

>>> list(filter(None, bool_list))
[True, True, True]
>>> len(list(filter(None, bool_list)))
3