Beginning Python - From Novice to Professional

CHAPTER 10 ■ BATTERIES INCLUDED 231
>>> from random import shuffle
>>> shuffle(deck)
>>> pprint(deck[:12])
['3 of spades',
'2 of diamonds',
'5 of diamonds',
'6 of spades',
'8 of diamonds',
'1 of clubs',
'5 of hearts',
'Queen of diamonds',
'Queen of hearts',
'King of hearts',
'Jack of diamonds',
'Queen of clubs']
Note that I’ve just printed the 12 first cards here, to save some space. Feel free to take a look at the whole deck
yourself.
Finally, to get Python to deal you a card each time you press Enter on your keyboard, until there are no more cards,
you simply create a little while loop. Assuming that you put the code needed to create the deck into a program file,
you could simply add the following at the end:
while deck: raw_input(deck.pop())
■Note If you try the while loop shown here in the interactive interpreter, you’ll notice that an empty string
gets printed out every time you press Enter because raw_input returns what you write (which is nothing),
and that will get printed. In a normal program, this return value from raw_input is simply ignored. To have
it “ignored” interactively, too, just assign the result of raw_input to some variable you won’t look at again
and name it something like ignore.
shelve
In the next chapter, you learn how to store data in files, but if you want a really simple storage
solution, the shelve module can do most of the work for you. All you have to do is supply it with
a file name. The only function of interest in shelve is open. When called (with a file name) it
returns a Shelf object, which you can use to store things. Just treat it as a normal dictionary
(except that the keys must be strings), and when you’re done (and want things saved to disk)
you call its close method.
A Potential Trap
It is important to realize that the object returned by shelve.open is not an ordinary mapping, as
the following example demonstrates: