Maybe a stupid question but I’m new to python.

The following code throws an error:

deck = [10, 2, 5, 8, 2, 7]
deck_idx = 0

def deal():
  card = deck[deck_idx]
  deck_idx += 1
  return card

print(deal())

Traceback (most recent call last):
File “main.py”, line 10, in
print(deal())
File “main.py”, line 6, in deal
card = deck[deck_idx]
UnboundLocalError: local variable ‘deck_idx’ referenced before assignment

while this doesn’t:

deck = [10, 2, 5, 8, 2, 7]
deck_idx = 0

def deal():
  card = deck[0]
  return card

print(deal())

10

both deck and deck_idx are declared in the same place, so I expect them to have the same visibility.

What am I missing here?