Python基本数据类型(列表)

旧城等待， 2021-12-24 03:35 427阅读 0赞

基本数据类型

**三、列表**

列表(List)是一个有序的Python对象序列。

**1.列表格式**

列表可以用一对中括号“\[ \]”生成，中间的元素用逗号“，”隔开：

li = [1,2,"alex"]

**2.列表的运算**

列表与字符串类似，支持相加和数乘。

列表相加，相当于将这两个列表按顺序连接：

li = [1,2,3] + ["alex",5]
    print(li)     #结果为：[1,2,3,"alex",5]

列表数乘，相当于将这个列表重复多次：

li = [1,2,"alex"] * 2
    print(li)     #结果为：[1, 2, 'alex', 1, 2, 'alex']

**3.索引和切片**

列表是个有序的序列，因此也支持索引和切片的操作。

索引：

li = [1,2,3,4,"alex"]
    print(li[0])        #结果为：1
    print(li[-1])        #结果为：alex

切片：

li = [1,2,3,4,"alex"]
    print(li[2:-1])      #结果为：[3,4]

与字符串不同，我们可以通过索引和切片来修改列表。

**4.元素的删除**

Python提供了一种更通用的删除列表元素的方法：关键字del。

li = [1,2,3,4,"alex"]
    del li[1]
    print(li)      #结果为：[1, 3, 4, 'alex']
    del li[1:-1]
    print(li)      #结果为：[1, 'alex']

**5.从属关系的判断**

可以用关键字in和not in判断某个元素是否在某个序列中。例如：对于列表

li = [1,2,3,4,"alex"]
    s = 2 in li
    print(s)     #结果为：True

**6.列表的方法**

列表一些常用的方法。

（1）.append()方法

.append()方法向列表追加单个元素。

li = [1,2,3,4,"alex"]
    li.append(5)
    print(li)      #结果为：[1, 2, 3, 4, 'alex', 5]

（2）.extend方法

.extend方法将另一个序列中的元素依次添加到列表。

li = [1,2,3,4,"alex"]
    li.extend([5,8])
    print(li)      #结果为：[1, 2, 3, 4, 'alex', 5, 8]

（3）.insert方法

.insert方法在指定索引位置插入元素。

li = [1,2,3,4,"alex"]
    li.insert(2,"hello")
    print(li)     #结果为：[1, 2, 'hello', 3, 4, 'alex']

（4）.remove方法

.remove方法将列表中第一个出现的指定元素删除，指定元素不存在会报错。

li = [1,2,3,4,"alex"]
    li.remove(3)
    print(li)     #结果为：[1, 2, 4, 'alex']

（5）.pop方法

.pop方法将列表中指定索引的元素删除，默认最后一个元素，并返回这个元素值。

li = [1,2,3,4,"alex"]
    a = li.pop(3)
    print(li)     #结果为：[1, 2, 3, 'alex']
    print(a)     #结果为：4

（6）.sort方法

.sort方法将列表中的元素按照从小到大排序。

li = [3,6,1,5,4]
    li.sort()
    print(li)     #结果为：[1, 3, 4, 5, 6]

可以在调用时加入一个reverse参数，如果它等于True，列表会按照从大到小进行排序：

li = [3,6,1,5,4]
    li.sort(reverse=True)
    print(li)      #结果为：[6, 5, 4, 3, 1]

（7）.reverse()方法

.reverse()方法将列表中的元素进行翻转。

li = [3,6,1,5,4]
    li.reverse()
    print(li)      #结果为：[4, 5, 1, 6, 3]

（8）.count方法

.count方法是计算列表的指定元素出现的次数。

li = [3,6,1,5,4,6]
    print(li.count(6))    #结果为：2

（9）.index方法

.index方法是获取指定元素第一次出现的索引位置。

li = [3,6,1,5,4,6]
    print(li.index(6))    #结果为：1

列表所有方法归纳：

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 class list(object):
      2     """
      3     list() -> new empty list
      4     list(iterable) -> new list initialized from iterable's items
      5     """
      6     def append(self, p_object): # real signature unknown; restored from __doc__
      7         """ L.append(object) -- append object to end """
      8         pass
      9 
     10     def count(self, value): # real signature unknown; restored from __doc__
     11         """ L.count(value) -> integer -- return number of occurrences of value """
     12         return 0
     13 
     14     def extend(self, iterable): # real signature unknown; restored from __doc__
     15         """ L.extend(iterable) -- extend list by appending elements from the iterable """
     16         pass
     17 
     18     def index(self, value, start=None, stop=None): # real signature unknown; restored from __doc__
     19         """
     20         L.index(value, [start, [stop]]) -> integer -- return first index of value.
     21         Raises ValueError if the value is not present.
     22         """
     23         return 0
     24 
     25     def insert(self, index, p_object): # real signature unknown; restored from __doc__
     26         """ L.insert(index, object) -- insert object before index """
     27         pass
     28 
     29     def pop(self, index=None): # real signature unknown; restored from __doc__
     30         """
     31         L.pop([index]) -> item -- remove and return item at index (default last).
     32         Raises IndexError if list is empty or index is out of range.
     33         """
     34         pass
     35 
     36     def remove(self, value): # real signature unknown; restored from __doc__
     37         """
     38         L.remove(value) -- remove first occurrence of value.
     39         Raises ValueError if the value is not present.
     40         """
     41         pass
     42 
     43     def reverse(self): # real signature unknown; restored from __doc__
     44         """ L.reverse() -- reverse *IN PLACE* """
     45         pass
     46 
     47     def sort(self, cmp=None, key=None, reverse=False): # real signature unknown; restored from __doc__
     48         """
     49         L.sort(cmp=None, key=None, reverse=False) -- stable sort *IN PLACE*;
     50         cmp(x, y) -> -1, 0, 1
     51         """
     52         pass
     53 
     54     def __add__(self, y): # real signature unknown; restored from __doc__
     55         """ x.__add__(y) <==> x+y """
     56         pass
     57 
     58     def __contains__(self, y): # real signature unknown; restored from __doc__
     59         """ x.__contains__(y) <==> y in x """
     60         pass
     61 
     62     def __delitem__(self, y): # real signature unknown; restored from __doc__
     63         """ x.__delitem__(y) <==> del x[y] """
     64         pass
     65 
     66     def __delslice__(self, i, j): # real signature unknown; restored from __doc__
     67         """
     68         x.__delslice__(i, j) <==> del x[i:j]
     69                    
     70                    Use of negative indices is not supported.
     71         """
     72         pass
     73 
     74     def __eq__(self, y): # real signature unknown; restored from __doc__
     75         """ x.__eq__(y) <==> x==y """
     76         pass
     77 
     78     def __getattribute__(self, name): # real signature unknown; restored from __doc__
     79         """ x.__getattribute__('name') <==> x.name """
     80         pass
     81 
     82     def __getitem__(self, y): # real signature unknown; restored from __doc__
     83         """ x.__getitem__(y) <==> x[y] """
     84         pass
     85 
     86     def __getslice__(self, i, j): # real signature unknown; restored from __doc__
     87         """
     88         x.__getslice__(i, j) <==> x[i:j]
     89                    
     90                    Use of negative indices is not supported.
     91         """
     92         pass
     93 
     94     def __ge__(self, y): # real signature unknown; restored from __doc__
     95         """ x.__ge__(y) <==> x>=y """
     96         pass
     97 
     98     def __gt__(self, y): # real signature unknown; restored from __doc__
     99         """ x.__gt__(y) <==> x>y """
    100         pass
    101 
    102     def __iadd__(self, y): # real signature unknown; restored from __doc__
    103         """ x.__iadd__(y) <==> x+=y """
    104         pass
    105 
    106     def __imul__(self, y): # real signature unknown; restored from __doc__
    107         """ x.__imul__(y) <==> x*=y """
    108         pass
    109 
    110     def __init__(self, seq=()): # known special case of list.__init__
    111         """
    112         list() -> new empty list
    113         list(iterable) -> new list initialized from iterable's items
    114         # (copied from class doc)
    115         """
    116         pass
    117 
    118     def __iter__(self): # real signature unknown; restored from __doc__
    119         """ x.__iter__() <==> iter(x) """
    120         pass
    121 
    122     def __len__(self): # real signature unknown; restored from __doc__
    123         """ x.__len__() <==> len(x) """
    124         pass
    125 
    126     def __le__(self, y): # real signature unknown; restored from __doc__
    127         """ x.__le__(y) <==> x<=y """
    128         pass
    129 
    130     def __lt__(self, y): # real signature unknown; restored from __doc__
    131         """ x.__lt__(y) <==> x<y """
    132         pass
    133 
    134     def __mul__(self, n): # real signature unknown; restored from __doc__
    135         """ x.__mul__(n) <==> x*n """
    136         pass
    137 
    138     @staticmethod # known case of __new__
    139     def __new__(S, *more): # real signature unknown; restored from __doc__
    140         """ T.__new__(S, ...) -> a new object with type S, a subtype of T """
    141         pass
    142 
    143     def __ne__(self, y): # real signature unknown; restored from __doc__
    144         """ x.__ne__(y) <==> x!=y """
    145         pass
    146 
    147     def __repr__(self): # real signature unknown; restored from __doc__
    148         """ x.__repr__() <==> repr(x) """
    149         pass
    150 
    151     def __reversed__(self): # real signature unknown; restored from __doc__
    152         """ L.__reversed__() -- return a reverse iterator over the list """
    153         pass
    154 
    155     def __rmul__(self, n): # real signature unknown; restored from __doc__
    156         """ x.__rmul__(n) <==> n*x """
    157         pass
    158 
    159     def __setitem__(self, i, y): # real signature unknown; restored from __doc__
    160         """ x.__setitem__(i, y) <==> x[i]=y """
    161         pass
    162 
    163     def __setslice__(self, i, j, y): # real signature unknown; restored from __doc__
    164         """
    165         x.__setslice__(i, j, y) <==> x[i:j]=y
    166                    
    167                    Use  of negative indices is not supported.
    168         """
    169         pass
    170 
    171     def __sizeof__(self): # real signature unknown; restored from __doc__
    172         """ L.__sizeof__() -- size of L in memory, in bytes """
    173         pass
    174 
    175     __hash__ = None
    176 
    177 list

list

转载于:https://www.cnblogs.com/lzc69/p/11032430.html

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