Modification of external vars in Python

nonlocal.py

# for closured vars
# we may use `nonlocal` keyword

def foo():

    a = 10
    b = 20

    def bar():
      nonlocal b # use parent "b"

      a = 20 # create local "a"
      b = 40 # modify outer "b"

    bar()

    print(a, b) # 10, 40

foo()

# this approach won't work in the global scope though
# and to modify global var, we should use directly
# modification of the globals() dict

a = 10
b = 20

def bar():
  # nonlocal b -- error

  a = 20 # create local "a"
  globals()['b'] = 40 # modify outer "b"

bar()

print(a, b) # 10, 40