CODEWITHSUNDEEP
python
Murshida Mouree
Murshida Mouree

Reputation: 3

Number of occurrences of a number in a list

This program below is supposed to count the number of occurrences of x in a list. Can not identify the error in the code

def count_x( items, x ):
    if items==[]:
        return 0
    first = items.pop(0)
    if first == x:
        return 1 + count_x(items, x)

Upvotes: 0

Views: 62

Answers (2)

Michael Cao
Michael Cao

Reputation: 3609

There are better ways to do this, but it's worth addressing why your code is throwing an error.

You don't have a case for when the item popped is not equal to your search item. This causes the function to return a None. Since it is working recursively, it tries to compute int + None, which leads to an error.

The other issue is that you are modifying the list with the function, which you may not want. For example:

def count_x( items, x ):
    print(items)
    if items==[]:
        return 0
    first = items.pop(0)
    if first == x:
        return 1 + count_x(items, x)
    
    else:
        return count_x(items, x)

items = [1, 2, 1, 1]

print(count_x(items, 1))

print(items)

Your items will become an empty list after you run the function.

Upvotes: 2

kaliiiiiiiii
kaliiiiiiiii

Reputation: 1135

I think it should work as following:

def count_x(items:list, x ):
    count = 0
    for item in items:
        if item == x:
            count = count + 1
    return count

count = count_x(items, x)

You could also simply use count = items.count(x) tho.

Upvotes: 0

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