Counter closure

---

examples/closures/counter.py

def create_counter():
    count = 0
    def internal():
        nonlocal count
        count += 1
        return count
    return internal

counter = create_counter()

print(counter())
print(counter())
print(counter())
print()

other = create_counter()
print(counter())
print(other())
print(counter())
print(other())

print()
print(count)

1
2
3

4
1
5
2

Traceback (most recent call last):
  File "counter.py", line 23, in <module>
    print(count)
NameError: name 'count' is not defined