Python Reading Notes : (2006-4-13)
Note One : the powerful Lists
Using Lists as Stacks
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To add an item to the top of the stack, use append() ,To retrieve an item from the top of the stack, use pop() without an explicit index. For example:
>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7
>>> stack
[3, 4, 5, 6]
>>> stack.pop()
6
>>> stack.pop()
5
>>> stack
[3, 4]
Using Lists as Queues
To add an item to the back of the queue, use append() To retrieve an item from the front of the queue, use pop() with 0 as the index. For example:
>>> queue = ["Eric", "John", "Michael"]
>>> queue.append("Terry")?????????? # Terry arrives
>>> queue.append("Graham")????????? # Graham arrives
>>> queue.pop(0)
'Eric'
>>> queue.pop(0)
'John'
>>> queue
['Michael', 'Terry', 'Graham']
Note?Two :about Tuples (distinguish between string type and? tuples tpye,especially?zero or only one items contained in a tuples?)
A special problem is the construction of tuples containing 0 or 1 items: the syntax has some extra quirks to accommodate these. Empty tuples are constructed by an empty pair of parentheses; a tuple with one item is constructed by following a value with a comma (it is not sufficient to enclose a single value in parentheses). Ugly, but effective. For example:
>>> empty = ()
>>> singleton = 'hello',??? # <-- note trailing comma
>>> len(empty)
0
>>> len(singleton)
1
>>> singleton
('hello',)
but if you write a statement like this :
>>> singleton = 'hello'????????? # it means that you define or construct a string type,not a tuples
>>>?singleton
'hello'
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