A python program to simulate a deck of cards.

a) First create a Card class with two attributes value and suit, where value can be anything from the list: 'ace', 'two', 'three' , 'four', 'five', 'six', 'seven', 'eight', 'nine', 'ten', 'jack', 'queen', 'king' (13 possibilities). Suit can be one of the four: 'clubs', 'diamonds', 'spades' and 'hearts'.

b) Add an __str__ method that prints the card in this format: Jack of Diamonds, Ace of Clubs etc.

c) In the main function, create a list containing 52 Card objects for a complete deck. You should have a nested loop to go through all 13 values and all 4 suits, each time creating a new Card object and pushing into the list.

d) Finally, display the deck by looping through all items in the list and calling print() on each card instance.