oneliner using reduce in python - python-3.x

Question

I'm trying to take my Python skills (beginner) to the next level.
and I'm trying to teach myself the functools.reduce() function
So I'm running every time into the same error;
I'd appreciate if someone could explain to me what is the problem in my code
I'm trying to build a simple func that receive a number and return the sum of number digits
import functools
def sum_using_reduce(number):
return str(number)[0] + str(number)[1]
number = 104
print(functools.reduce(sum_using_reduce, number))

Answer 1

Try this:
number = 104
functools.reduce(lambda x, y: x+y, [int(i) for i in str(number)])
Output: 5
Using your example:
import functools
def sum_using_reduce(x, y) -> int:
return x + y
print(functools.reduce(sum_using_reduce, [int(i) for i in str(105)]))
Output: 6
Another approach:
import functools
def sum_using_reduce(number: int) -> int:
return functools.reduce(lambda x, y: x+y, [int(i) for i in str(number)])
print(sum_using_reduce(124))
Output: 7

Answer 2

In your sum_using_reduce function you are trying to sum two strings, which would simply perform concatenation. Moreover, you are providing an integer as the second argument to the reduce function, where the reduce function requires an iterable to be provided.
Below is a solution that fixes both these requirements:
from functools import reduce
number=104
print(reduce(lambda x,y:x+y,map(int,str(number))))
map(int,str(number)) transforms the number to a string (104->"104") and then turns every character in the string to an integer, returning an iterable map object ("104"->[1,0,4]).
lambda x,y:x+y is a function which takes two integers and sums them.