Python Recursion (task 16.2 python intermediate)

Question

This is the right solution. If anybody can please explain why it is like that and what exactly happens. I tried to understand but i dont get it.

What does the „* 10“ do?
How exactly does the recursion works in this case?

def convert(num):
if num==0:
return 0
return (num % 2 + 10 * convert(num // 2))

print(convert(int(input())))

Answer 1

convert(num) is returns either 0 or 1 each time.
There 10* convert is used to append next result to previous one.

Ex: 5
1+10*( convert (2) )
1+10*( 0+10*(convert(1)))
1+10*(0+10*(1+10*convert(0)))
1+10*(0+10*(1+10*0))
1+10*(0+10)
1+100
= 101

Ex: 3
1+10*( 1+10*0) = 1+10=11

Answer 2

Okay ty but wouldnt this lead to an infinite recursion since the recursion continues forever. Even if num is 0 convert(num//2) always gives 0 but can continue doesnt it?

Answer 3

Ah yes thank you. Was so deep in the recursion forgot about the if condition

Answer 4

If num==0 : return 0 is the base or stop condition. Without this, it will lead to infinite recursion. It stopping call further recursion.
convert(0) returns 0 , does not call again convert(0//2)