Simple Python problem #1 --- pair, car, and cdr

carncdr.py

# Problem Statement 
# cons(a, b) constructs a pair, and car(pair) and cdr(pair) returns the first and last element of that pair.
# For example, car(cons(3, 4)) returns 3, and cdr(cons(3, 4)) returns 4.
# Given the below implementation for cons( ), please implement car & cdr

def cons(a, b):
  def pair(f):
    return f(a, b)
  return pair

def car (f) :
  return f(lambda x, y : x)

def cdr (f) :
  return f(lambda x, y : y)