Unable to use *= python operator in list comprehension [duplicate]

Answer 1

Alternatively, you can approach it with reduce() and filter():

>>> from operator import mul
>>> from functools import reduce  # needed if Python 3.x
>>>
>>> l = [-1, 2, 4, 1, -3]
>>> reduce(mul, filter(lambda x: x < 0, l), 1)
3

A related tip: one of the indicators for using reduce() is that you have multiple values, but need to produce a single value out of it.

Answer 2

The assignment operator (and all variations on it) forms a statement in Python, not an expression. Unfortunately, list comprehensions (and other comprehensions, like set, dictionary and generators) only support expressions.