The next gotcha involves short-circuiting.

>>> a = [2, 1, 3, 4, 7, 11]

This pops one value because x() or y() won't run y() if x() evaluates to something truthy:
>>> a.pop() or a.pop()
11
>>> a
[2, 1, 3, 4, 7]

This pops twice though:
>>> a.pop() and a.pop()
4
>>> a
[2, 1, 3]

And note that "a or b" and "a and b" will return the actual *value* (which may be the booleans True or False or might be some other value!)