CODEWITHSUNDEEP
pythonlistcount
Mordoxalandier
Mordoxalandier

Reputation: 17

How to count the number of elements in a list?

I need to write a python function that will count all the elements in a list, including those elements in a nested list.

Example, len() is built in function, at_len() is the function I want to create:

len( [1, 2] )  ---> 2

at_len( [1, 2] ) ---> 2

len( [ [1, 2], 3 ] ) ---> 2

at_len( [ [1, 2], 3 ] ) ---> 3

len( [1, 2, 'three', [1, 2, 3, ['a', 'b'] ], 5] )  --> 5

at_len( [1, 2, 'three', [1, 2, 3, ['a', 'b'] ], 5] )  --> 9

I need to be able to count those elements that are in nested lists. This is the code that I have, as well as the output I am getting.

def at_len(element_list):
    count = 0
    for each_item in element_list:
            if isinstance(each_item, list):
                    at_len(each_item)
            else:
                    count = count + 1
    print(count)

output: 

at_len(['hello',1,2,'three',[1,'two',3]]) --> 3, 4 (should be 7)

at_len([1,2,[1,2,3]]) --> 3, 2 (should be 5)

I think I am close, but for some reason it prints out two counts instead of having them added together to get the correct total.

Upvotes: 1

Views: 3134

Answers (2)

Grismar
Grismar

Reputation: 31319

The whole function is really nothing more than:

def at_len(xs):
    return sum(at_len(x) for x in xs) if isinstance(xs, list) else 1

Or if you need it to not just work for lists:

from typing import Iterable


def at_len(xs):
    return sum(at_len(x) for x in xs) if isinstance(xs, Iterable) else 1

Upvotes: 0

Joel
Joel

Reputation: 23827

Replace at_len(each_item) by count += at_len(each_item) and then return count (instead of printing).

It's printing twice because of the recursive call. The print command is within the function. Also notice that total is given a value but never used. Instead do it as

def at_len(element_list):
    count = 0
    for each_item in element_list:
            if isinstance(each_item, list):
                    count += at_len(each_item)
            else:
                    count += 1
    return count

then just call it as:

print(at_len(yourlist))

Upvotes: 4

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