Python 闭包的使用方法

def print_msg(msg):
# This is the outer enclosing function

  def printer():
# This is the nested function
    print(msg)

  printer()

# We execute the function
# Output: Hello
print_msg("Hello")

def print_msg(msg):
# This is the outer enclosing function

  def printer():
# This is the nested function
    print(msg)

  return printer # this got changed

# Now let's try calling this function.
# Output: Hello
another = print_msg("Hello")
another()

> del print_msg
> another()
Hello
> print_msg("Hello")
Traceback (most recent call last):
...
NameError: name 'print_msg' is not defined

 
def make_multiplier_of(n):
  def multiplier(x):
    return x * n
  return multiplier

# Multiplier of 3
times3 = make_multiplier_of(3)

# Multiplier of 5
times5 = make_multiplier_of(5)

# Output: 27
print(times3(9))

# Output: 15
print(times5(3))

# Output: 30
print(times5(times3(2)))

> make_multiplier_of.__closure__
> times3.__closure__
(<cell at 0x0000000002D155B8: int object at 0x000000001E39B6E0>,)

> times3.__closure__[0].cell_contents
3
> times5.__closure__[0].cell_contents
5