python closure

python_closure.py

def computer():
    count = 5
    def plus(num):
        count += num
        print count
    return plus
plus = computer()
plus(3)
plus(5)
"""
Traceback (most recent call last):
  File "closure.py", line 8, in <module>
    plus(3)
  File "closure.py", line 4, in plus
    count += num
UnboundLocalError: local variable 'count' referenced before assignment
"""


class Hello():
    @classmethod
    def computer(cls):
        count = 5
        def plus(num):
            # or count += num
            v = count + num
            count = v
            print count
        return plus

plus = Hello.computer()
plus(3)
plus(4)

"""
Traceback (most recent call last):
  File "closure.py", line 12, in <module>
    plus(3)
  File "closure.py", line 6, in plus
    v = count + num
UnboundLocalError: local variable 'count' referenced before assignment
"""

class Hello():
    @classmethod
    def computer(cls):
        count = 5
        def plus(num):
            print count + num
        return plus

plus = Hello.computer()
plus(3)
plus(4)
"""
8
9
"""