如何从 python 中的列表中只获取负数

Question

I'm trying to make def get_neg(): so that get_neg(lst) returns "-1, -2, -3" when lst = [-1, -2, -3, 4, 5, 6]. I tried this code below, but I don't know how to get the result in 1 line.

def get_neg():
    for n in lst:
        if n < 0:
            print(str(n) + ',')
        else:
            pass

This way I get each numbers in a different row and a comma at the end. It has to be programmed with basic commands

Answer 1

You can use list comprehensions (Do not forget to give lst as an argument to the get_neg function):

def get_neg(lst):
    return [x for x in lst if x < 0]

Example

get_neg([-1,-2,4,5]) # [-1, -2]
get_neg([-15,-22,-4, 5, 0]) # [-15, -22, -4]