Python Native Datatypes -- list
>>>li=[ " a " ," b " ," mpilgrim " ," z " ," example " ]>>>li
[ ' a ' ,' b ' ,' mpilgrim ' ,' z ' ,' example ' ]
>>>li
' a '
>>>li[ 4 ]
' example '
1、list的元素是有序的
2、list可以当成数组来用，元素下标从0开始
>>> li
['a', 'b', 'mpilgrim', 'z', 'example']
>>> li[−1]
'example'
>>> li[−3]
'mpilgrim'
3、list的索引可以是负数，表达式L的含义为：
（1）当0 <= n <= len(L)-1 时， 跟java、C中的数组元素索引一样
（2）当-len(L) <= n <= -1 时, L = L
（3）n不再上述范围内是，程序引发IndexError
li = ['a', 'b', 'String', 'list', 'dictionary']
print li
print li[:]
print li[:3]
print li
print li # won't cause IndexError
print li[-2:-1] # identical to li=li
print li[-1:-2] # identical to li, so it will return a empty list
print li[-125:1159]
运行结果：
['a', 'b', 'String']
['a', 'b', 'String', 'list', 'dictionary']
['a', 'b', 'String']
['b', 'String', 'list', 'dictionary']
['a', 'b', 'String', 'list', 'dictionary']
['list']
[]
['a', 'b', 'String', 'list', 'dictionary']
4、L（其中a,b为整数）表示一个分片操作，注意a，b可以是任意的整数，而且分片操作永远不会引发IndexError。但是a，b取不同的值时，程序行为稍有不同。
（1）当 0 <= a < b < len(L)时，L返回一个由L, L...L组成的list
（2）当 0 <= b <= a < len(L)时，L返回空的list
（3）当a，b取值不在上述范围时，应用以下4条规则替换a，b的值，得到a，b新的值后再应用上面两条规则。
[*]若 a >= len(L), 则 a = len(L)-1
[*]若 -len(L) <= a < 0, 则 a = len(L) + a
[*]若 a < -len(L)， 则 a = 0
[*]b的情况跟a一样
[*]当 a没有指定时，a = 0, 当b没指定时，b=len(L)-1
5、append和extend方法的不同，看下例就一目了然了。
>>> li = ['a', 'b', 'c']
>>> li.extend(['d', 'e', 'f'])
>>> li
['a', 'b', 'c', 'd', 'e', 'f']
>>> len(li)
6
>>> li[−1]
'f'
>>> li = ['a', 'b', 'c']
>>> li.append(['d', 'e', 'f'])
>>> li
['a', 'b', 'c', ['d', 'e', 'f']]
>>> len(li)
4
>>> li[−1]
['d', 'e', 'f'
注意 extend的参数不仅仅可以是list，也可以是一个tuple, dictionary等可以iterable的数据结构
6、
List object methods
Method
Description
Nonmutating methods
L
.count(
x
)
Returns the number of items of L
that are equal
to x
.
L
.index(
x
)
Returns the index of the first occurrence of an item in
L
that is equal to x
, or raises an exception if
L
has no such item.
Mutating methods
L
.append(x
)
Appends item x
to the end of L
; e.g.,
L
[len(
L
):]=[
x
]
.
L
.extend(s
)
Appends all the items of iterable s
to the end
of L
; e.g.,
L
[len(
L
):]=
s
.
L
.insert(i, x
)
Inserts item x
in L
before the
item at index i
, moving following items of L
(if
any) "rightward" to make space (increases
len(
L
)by one, does not replace any item, does
not raise exceptions: acts just like
L
[
i
:
i
]=[
x
]
).
L
.remove(x
)
Removes from L
the first occurrence of an item
in L
that is equal to x
, or raises an exception
if L
has no such item.
L
.pop([i
])
Returns the value of the item at index i
and
removes it from L
; if i
is omitted, removes and
returns the last item; raises an exception if L
is empty or
i
is an invalid index in L
.
L
.reverse( )
Reverses, in place, the items of
L
.
L
.sort([
f
])(2.3)
Sorts, in place, the items of L
, comparing
items pairwise via function f
; if f
is omitted,
comparison is via the built-in function cmp
. For more details, see "Sorting a list
" on page
57.
L
.sort(cmp=cmp, key=None,
reverse=False)
(2.4)
Sorts, in-place, the items of L
, comparing
items pairwise via the function passed as cmp
(by default, the
built-in function cmp
). When argument key
is not
None
, what gets compared for each item x
is
key
(
x
)
, not x
itself. For more details, see "Sorting a list
" on page
57.
7、
>>> li = ['a', 'b', 'mpilgrim']
>>> li = li + ['example', 'new']
>>> li
['a', 'b', 'mpilgrim', 'example', 'new']
>>> li += ['two']
>>> li
['a', 'b', 'mpilgrim', 'example', 'new', 'two']
>>> li = * 3
>>> li
注意下面的例子：
li = ['a']
print li
#li = li + 'b'TypeError: can only concatenate list (not "str") to list
li += 'b'
print li
li = li * 2
print li
li *= 2
print li
运行结果：
['a']
['a', 'b']
['a', 'b', 'a', 'b']
['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']
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