从父级的 function scope 覆盖变量

Question

I'm trying to write a recursive function. When i write code like this one. It works fine.

def older_func():
    variable = 1
    def func():
       print(variable)

       return func

    return func
older_func()(5)

But if I try to reassign my variable after printing i get an error

def older_func():
    variable = 1
    def func(n):
       print(variable)
       variable = n
       return func

    return func
older_func()(5)

local variable referenced before assignment. on printing step. Please help me understand behavior and way to overcome this.

UnboundLocalError: local variable 'variable' referenced before assignment

Answer 1

There is no error code just returns a function object because you don't call the actual function you Just return it return func

but when you call it return func(n) it will raise UnboundLocalError: local variable 'variable' referenced before assignment so you need to use nonlocal Keyword

def older_func():
   variable = 1

   def func(n):
      nonlocal variable
      print(variable)
      variable = n
      return func

   return func(5)