I got the following code:
f = lambda y, z: filter(y, z)
g = lambda x: [x for x in range(int(x**0.5))]
r = f(g, g(11))
I was wondering how r ended up being [1,2].
I understand why g(11) is [0,1,2] but I didn't quite catch how the filter function works here.
After doing all necessary replacements, the functions above can be simplified to
filter(lambda x: [x for x in range(int(x**0.5))], [0, 1, 2])
Now for x=0, the list will be empty (since [x for x in range(int(0**0.5))] is an empty list due to range(0)), and hence will evaluate to False, and for x=1,2 it will evaluate to True since it will be non-empty.
filter constructors the iterator based on the elements for which the function returns True, hence 0 is filtered out of the list and we get [1,2] as the output of the filter function