Python Native Datatypes -

jefflee

>>>  li  =  [ " a " ,  " b " ,  " mpilgrim " ,  " z " ,  " example " ]>>>  li[ ' a ' ,  ' b ' ,  ' mpilgrim ' ,  ' z ' ,  ' example ' ]>>>  li[0]' 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[n]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[n] = L[len(L)+n]
（3）n不再上述范围内是，程序引发IndexError
li = ['a', 'b', 'String', 'list', 'dictionary']print li[0:3]print li[:]print li[:3]print li[1:]print li[0:7] # won't cause IndexErrorprint li[-2:-1] # identical to li[len(li)-2 : len(li)-1]=li[3:4]print li[-1:-2] # identical to li[4:3], so it will return a empty listprint 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[a:b]（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[a:b]返回一个由L[a], L[a+1]...L[b-1]组成的list
（2）当 0 <= b <= a < len(L)时，L[a:b]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 = [1, 2] * 3>>> li[1, 2, 1, 2, 1, 2] 注意下面的例子：
li = ['a']print li#li = li + 'b'  TypeError: can only concatenate list (not "str") to listli += 'b'print lili = li * 2                      print lili *= 2print li 运行结果：
['a']['a', 'b']['a', 'b', 'a', 'b']['a', 'b', 'a', 'b', 'a', 'b', 'a', 'b']