list的深入学习

CUDev

5.1 More on Lists
The list data type has some more methods.  Here are all of the methods
of list objects:
  append(
  x)
Add an item to the end of the list;
equivalent to a[len(a):] = [x].
  extend(
  L)
Extend the list by appending all the items in the given list;
equivalent to a[len(a):] = L.
  insert(
  i, x)
Insert an item at a given position.  The first argument is the index
of the element before which to insert, so a.insert(0, x)
inserts at the front of the list, and a.insert(len(a), x)
is equivalent to a.append(x).
  remove(
  x)
Remove the first item from the list whose value is x.
It is an error if there is no such item.
  pop(
  )
Remove the item at the given position in the list, and return it.  If
no index is specified, a.pop() removes and returns the last item
in the list.  The item is also removed from the list.  (The square brackets
around the i in the method signature denote that the parameter
is optional, not that you should type square brackets at that
position.  You will see this notation frequently in the
Python Library Reference
.)
  index(
  x)
Return the index in the list of the first item whose value is x.
It is an error if there is no such item.
  count(
  x)
Return the number of times x appears in the list.
  sort(
  )
Sort the items of the list, in place.
  reverse(
  )
Reverse the elements of the list, in place.
An example that uses most of the list methods:
>>> a = [66.25, 333, 333, 1, 1234.5]
>>> print a.count(333), a.count(66.25), a.count('x')
2 1 0
>>> a.insert(2, -1)
>>> a.append(333)
>>> a
[66.25, 333, -1, 333, 1, 1234.5, 333]
>>> a.index(333)
1
>>> a.remove(333)
>>> a
[66.25, -1, 333, 1, 1234.5, 333]
>>> a.reverse()
>>> a
[333, 1234.5, 1, 333, -1, 66.25]
>>> a.sort()
>>> a
[-1, 1, 66.25, 333, 333, 1234.5]
5.1.1 Using Lists as Stacks
The list methods make it very easy to use a list as a stack, where the
last element added is the first element retrieved (``last-in,
first-out'').  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]
5.1.2 Using Lists as Queues
You can also use a list conveniently as a queue, where the first
element added is the first element retrieved (``first-in,
first-out'').  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']
               
               
               

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