JuniorTheoryCommon

What happens when this program runs?

Python

names = {}
point = [1, 2]
print("start")
names[point] = "A"
print(names)

Prints start, then a TypeError

Expecting {[1, 2]: 'A'}: a dict key must be hashable, and a list can change, so it is not. The line raises TypeError: unhashable type: 'list'.
Expecting nothing to print: the TypeError happens while the program runs, so start prints first and the program stops at names[point] = "A".

JuniorTheoryCommon

Python

names = {}
point = [1, 2]
print("start")
names[point] = "A"
print(names)

Prints start, then a TypeError

Expecting {[1, 2]: 'A'}: a dict key must be hashable, and a list can change, so it is not. The line raises TypeError: unhashable type: 'list'.
Expecting nothing to print: the TypeError happens while the program runs, so start prints first and the program stops at names[point] = "A".