Local vs NonLocal Scope Python

Question

I am trying to understand scopes in Python and am confused in the examples below (I am using Python 3.12.2) -

1.

a = 10

def myfunc():
    a = 2
    print(a)

print(a)
myfunc()

This gives the output -

10
2

a = 10

def myfunc():
    print(a)

print(a)
myfunc()

This gives the output -

10
10

3. However, when I do this -

a = 10

def myfunc():
    print(a)
    a = 2

print(a)
myfunc()

UnboundLocalError: cannot access local variable 'a' where it is not associated with a value

I am not sure how this is different from code example 1. Why is my output not-

10
10