Python初学3-组/序列

约定不等于承诺〃 2022-05-23 13:04 181阅读 0赞

组概念

**1.列表**

列表形式

>>> type([1,2,3,4,5,6])
    <type 'list'>
    >>> type([1,True,'aaaa'])
    <type 'list'>
    >>> type([[1,2],[True,'aaa'],[3,'bbb',False]]) //嵌套列表
    <type 'list'>

列表获取元素

>>> ['aaa','bbbbb','cccc'][0]
    'aaa'
    >>> ['aaa','bbbbb','cccc'][0:2]
    ['aaa', 'bbbbb']
    >>> ['aaa','bbbbb','cccc'][0][1]
    'a'

列表运算

>>> [1,True,'abc']+['aaa','bbbbb','cccc']
    [1, True, 'abc', 'aaa', 'bbbbb', 'cccc']
    >>> [1,True,'abc']*2
    [1, True, 'abc', 1, True, 'abc']

**2.元组**

>>> type((1,True,'abc'))
    <type 'tuple'>
    >>> (1,True,'abc')
    (1, True, 'abc')
    >>> (1,True,'abc')[0]
    1
    >>> (1,True,'abc')[0:2]
    (1, True)
    >>> (1,True,'abc')[2][1]
    'b'

<type 'tuple'>
    >>> type((1))
    <type 'int'>
    >>> type(('hello'))
    <type 'str'>
    >>> type((True))
    <type 'bool'>
    
    此时Python将()作为运算符

**3.set集合**

** ** 特点1：数据类型唯一

>>> type({1,True.'abc'})
    SyntaxError: invalid syntax
    >>> type({1,2,3})
    <type 'set'>

特点2：数据无序

>>> {1,2,3,4}[0]
    
    Traceback (most recent call last):
      File "<pyshell#3>", line 1, in <module>
        {1,2,3,4}[0]
    TypeError: 'set' object does not support indexing
    >>> {1,2,3,4}[0:1]
    
    Traceback (most recent call last):
      File "<pyshell#4>", line 1, in <module>
        {1,2,3,4}[0:1]
    TypeError: 'set' object has no attribute '__getitem__'
    >>>

特点3：不重复

>>> {1,1,2,2,2,3,3,3,3}
    set([1, 2, 3])

集合运算

>>> {1,2,3,4,5,6}-{5,6}
    set([1, 2, 3, 4])
    >>> {1,2,3,4,5,6}-{5,6,7,8}
    set([1, 2, 3, 4])
    >>> {1,2,3,4,5,6}&{5,6}
    set([5, 6])
    >>> {1,2,3,4,5,6}|{5,6}
    set([1, 2, 3, 4, 5, 6])
    >>> {1,2,3,4,5,6}|{5,6,7,8}
    set([1, 2, 3, 4, 5, 6, 7, 8])

空集

>>> type({})
    <type 'dict'>
    >>> type(set())
    <type 'set'>
    >>> len(set())
    0

**4.字典**

key(object):value(object)

type({1:1,2:True,3:'abc',True:5,'abc':False})
    <type 'dict'>

>>> {1:1,2:True,3:'abc',True:5,'abc':False}[1]
    5                        //有问题
    >>> {1:1,2:True,3:'abc',True:5,'abc':False}[2]
    True
    >>> {1:1,2:True,3:'abc',True:5,'abc':False}[3]
    'abc'
    >>> {1:1,2:True,3:'abc',True:5,'abc':False}[True]
    5
    >>> {1:1,2:True,3:'abc',True:5,'abc':False}['abc']
    False
    >>> {1:1,2:True,3:'abc',True:5,'abc':False}['aaaaaaaaa']
    
    Traceback (most recent call last):
      File "<pyshell#15>", line 1, in <module>
        {1:1,2:True,3:'abc',True:5,'abc':False}['aaaaaaaaa']
    KeyError: 'aaaaaaaaa'
    >>>