如果列表中没有负数，Python如何打印0？

Question

I have to print the first negative number in a list, but if there are no negative numbers I have to return it as 0. I cannot for the life of me figure this out, I feel very dumb.

def find_negative(list_numbers):
    for list_number in list_numbers:
        if list_number < 0:
            return list_number

Currently it works if there are negative numbers, but if there aren't, it'll return nothing. I can't seem to make it so it returns 0 instead of nothing

Answer 1

You can use this one-liner:

num = next((x for x in numbers if x < 0), 0)

There's a little package on PyPI providing the first() function which might be more convenient:

from first import first    
num = first(numbers, key=lambda x: x < 0, default=0)

Answer 2

Add return 0 outside of the for loop. The program arrives there only if it didn't find any negative number.

def find_negative(list_numbers):
    for list_number in list_numbers:
        if list_number < 0:
            return list_number
    return 0

Answer 3

try this:

def find_negative(list_numbers):
    first_index = 0
    for list_number in list_numbers:
        if list_number < 0:
            first_index = list_number
            break
    return first_index

Answer 4

Your code works fine if you do this to return the first negative number in the list but it doesn't mention any else thing to do if the condition is not met ie if there are no negative numbers. so you can use another variable which can be zero initially and will become equal to list_number if there is a negative number and remain zero only if there are no negative numbers in the list.

def find_negative(list_numbers): Number=0 for list_number in list_numbers: if list_number < 0: Number= list_number break return Number

In the above code, the loop will break once it encounters a negative number and will return the index of that number and if it doesn't come across a negative number, it will return a zero.