So why does this code not print previous example as a list? (Please!)

Question

def countdown():
i=5
while i > 0:
yield i
i -= 1

for i in countdown():
print(list(countdown(i)))

Answer 1

Because countdown() iterator takes no arguments. And you are calling it with one: countdown(i). You should ether iterate countdown or list it, not both:

>>> for i in countdown(): #iterate countdown
print(i)

5
4
3
2
1

>>> print(list(countdown())) #list countdown
[5, 4, 3, 2, 1]

Answer 2

countdown(i) won't work.

If you want countdown to take a parameter with a default value, you should use

def countdown(i = 5):
while i > 0:
...