Assign function as function's method.

fn_assign_fn.py

def foo(a, b, c):
  print(a, b, c)
  
def get_n():
  print("get_n()")
  
def put_n():
  print("put_n()")
  
foo.get_n = get_n
foo.put_n = put_n

foo.get_n()
foo(1, 2, 3)
foo.put_n()

# 結果:
# get_n()
# (1, 2, 3)
# put_n()