2020.06.18--预习课--第6节--字符串、元组、列表、字典

一、列表

1、增

1.1、追加增

>>> list_1 = []
>>> list_1.append('a')
>>> list_1
['a']
>>> list_1.append(100)
>>> list_1
['a', 100]
>>> list_1.append([])
>>> list_1.append({})
>>> list_1.append(())
>>> list_1
['a', 100, [], {}, ()]
>>>

1.2、定位增，索引可以越界

>>> list_1
['a', 100, [], {}, ()]
>>> list_1.insert(1,'x')
>>> list_1
['a', 'x', 100, [], {}, ()]
>>> list_1.insert(1,'y')
>>> list_1
['a', 'y', 'x', 100, [], {}, ()]
>>> list_1.insert(1,'z')
>>> list_1
['a', 'z', 'y', 'x', 100, [], {}, ()]
>>> list_1.insert(100,100)
>>> list_1
['a', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2, 3, 100]
>>> 

1.3、extend

>>> list_1
['a', 'z', 'y', 'x', 100, [], {}, ()]
>>> list_2 = [1,2,3]
>>> list_1.append(list_2)
>>> list_1
['a', 'z', 'y', 'x', 100, [], {}, (), [1, 2, 3]]
>>> list_1.extend(list_2)
>>> list_1
['a', 'z', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2, 3]
>>>

2、删

2.1、单个删，索引不可以越界

>>> list_1
['a', 'z', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2, 3]
>>>
>>> del list_1[1]
>>> list_1
['a', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2, 3]
>>> del list_1[100]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range
>>> 

2.2、切片删

>>> list_1
['a', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2, 3, 100]
>>> del list_1[10:100]
>>> list_1
['a', 'y', 'x', 100, [], {}, (), [1, 2, 3], 1, 2]
>>> del list_1[1:3]
>>> list_1
['a', 100, [], {}, (), [1, 2, 3], 1, 2]
>>>

2.3、删除整个变量

>>> list_2
[1, 2, 3]
>>> del list_2
>>> list_2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'list_2' is not defined
>>>

3、改

3.1、单个改，索引不可越界

>>> list_1
['a', 100, [], {}, (), [1, 2, 3], 1, 2]
>>> list_1[1]='xyz'
>>> list_1
>>> list_1[100] = 100
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range
>>> 

3.2、切片改

>>> list_1
['a', 'xyz', [], {}, (), [1, 2, 3], 1, 2]
>>> list_1[1:5]='xyz'    # 切片长度大于赋值内容长度，没有内容的为空，具体表现等于与删除了
>>> list_1
['a', 'x', 'y', 'z', [1, 2, 3], 1, 2]
>>> list_1[1:3]='xyzUniden'    # 切片长度小于赋值内容长度，没有索引的部分，具体表现等同于插入
>>> list_1
['a', 'x', 'y', 'z', 'U', 'n', 'i', 'd', 'e', 'n', 'z', [1, 2, 3], 1, 2]
>>> 

4、查

>>> list_1
['a', 'x', 'y', 'z', 'U', 'n', 'i', 'd', 'e', 'n', 'z', [1, 2, 3], 1, 2]
>>> list_1[0]
'a'
>>> list_1[1]
'x'
>>> list_1[2]
'y'
>>> list_1[3]
'z'
>>> list_1[300]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>> 

二、元组

1、定义元组时，只有一个元素是，必须要加一个逗号

>>> t = ('a')
>>> t
'a'
>>> type(t)
<class 'str'>
>>> t_1 = ([1,2,3])
>>> t_1
[1, 2, 3]
>>> type(t_1)
<class 'list'>
>>> t_2 = ({1:'a'})
>>> t_2
{1: 'a'}
>>> type(t_2)
<class 'dict'>
>>>

>>> t = ('a',)
>>> t
('a',)
>>> type(t)
<class 'tuple'>
>>> t_1 = ([1,2,3],)
>>> t_1
([1, 2, 3],)
>>> type(t_1)
<class 'tuple'>
>>> t_2 = ({1:'a'},)
>>> t_2
({1: 'a'},)
>>> type(t_2)
<class 'tuple'>
>>> t_3 = (1,)
>>> t_3
(1,)
>>> type(t_3)
<class 'tuple'>
>>> 

2、元组只能查，不能增、删、改

2.1、单个查找，索引不可越界

>>> t
(1, 2, 3, 'a', 'b', 'c', [1, 2], {1: 'a'}, 1.1, 2.2)
>>> t[0]
1
>>> t[1]
2
>>> t[2]
3
>>> t[3]
'a'
>>> t[5]
'c'
>>> t[500]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: tuple index out of range
>>>

 

2.2、可以切片查找

>>> t
(1, 2, 3, 'a', 'b', 'c', [1, 2], {1: 'a'}, 1.1, 2.2)
>>> t[5:9]
('c', [1, 2], {1: 'a'}, 1.1)
>>> t[5:90]
('c', [1, 2], {1: 'a'}, 1.1, 2.2)
>>>

 

 2.3、所有元组的子元素的地址，是不能改变的

>>> t
(1, 2, 3, 'a', 'b', 'c', [1, 2, 10], {1: 'a'}, 1.1, 2.2)
>>> t[6]
[1, 2, 10]
>>> t[6].append('x')
>>> t
(1, 2, 3, 'a', 'b', 'c', [1, 2, 10, 'x'], {1: 'a'}, 1.1, 2.2)
>>> id(t[6])
4526153032
>>> t[6].append('x_1')
>>> t
(1, 2, 3, 'a', 'b', 'c', [1, 2, 10, 'x', 'x_1'], {1: 'a'}, 1.1, 2.2)
>>> id(t[6])
4526153032
>>> t[6]=[1,2,3,4]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> 

三、字典

1、字典的key不可以重复，如果赋值重复了，会把value替换掉

>>> d = {1:2,3:4,5:6,7:8}
>>> d
{1: 2, 3: 4, 5: 6, 7: 8}
>>> d[1]=100
>>> d
{1: 100, 3: 4, 5: 6, 7: 8}
>>> d[2] = 'a'
>>> d
{1: 100, 3: 4, 5: 6, 7: 8, 2: 'a'}
>>> d[1] = 'abc'
>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a'}
>>>

 

2、key只能是不可变类型

>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a'}
>>> d[[1,2,3]] = [1,2,3]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'list'
>>> d[(1,2,3)] = [1,2,3]
>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a', (1, 2, 3): [1, 2, 3]}
>>> d[{1:2}] = 100
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unhashable type: 'dict'
>>>

 

3、遍例字典

3.1、遍例字典的key

>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a', (1, 2, 3): [1, 2, 3]}
>>> d.keys()
dict_keys([1, 3, 5, 7, 2, (1, 2, 3)])
>>>

 

3.2、遍例字典的value

>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a', (1, 2, 3): [1, 2, 3]}
>>> d.values()
dict_values(['abc', 4, 6, 8, 'a', [1, 2, 3]])
>>>

 

3.3、遍例字典的key和value

>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a', (1, 2, 3): [1, 2, 3]}
>>> for k,v in d.items():
...     print('key:',k,';value:',v)
...
key: 1 ;value: abc
key: 3 ;value: 4
key: 5 ;value: 6
key: 7 ;value: 8
key: 2 ;value: a
key: (1, 2, 3) ;value: [1, 2, 3]
>>>

 

4、批量操作

4.1、批量修改，将value全部修改为’change‘

>>> d
{1: 'abc', 3: 4, 5: 6, 7: 8, 2: 'a', (1, 2, 3): [1, 2, 3]}
>>> d_key = list(d.keys())
>>> d_key
[1, 3, 5, 7, 2, (1, 2, 3)]
>>> for i in d_key:
...     d[i] = 'change'
...
>>> d
{1: 'change', 3: 'change', 5: 'change', 7: 'change', 2: 'change', (1, 2, 3): 'change'}
>>>

 

 

4.2、批量删除，成为一个空字典

>>> d
{1: 'change', 3: 'change', 5: 'change', 7: 'change', 2: 'change', (1, 2, 3): 'change'}
>>> d_key = list(d.keys())
>>> d_key
[1, 3, 5, 7, 2, (1, 2, 3)]
>>> for i in d_key:
...     del d[i]
...
>>> d
{}
>>>

四、习题

练习一：

count函数的算法
算法：
    1 定义一个函数，参数传递一个字符串
    2 声明一个变量letter_count存储某个字符出现的个数
    3 遍历字符串，逐一拿出来，判断是否是你想要统计的那个
    4 如果是，则letter_count+1
    5 如果不是，则什么都不做
    6 把函数中的统计结果变量返回回来 return letter_count

def count_1(msg, s):
    letter_count = 0
    for i in msg:
        if i == s:
            letter_count += 1
    return letter_count


count_content = input("请输入要统计的原内容>>：")
str_count = input("请输入需要统计的字符>>：")
print(count_1(count_content, str_count))

练习二：

选做：
abcxabcyabc，请统计一下abc有多少个？用函数实现

def count_2(msg, s):
    str_count = 0
    s_long = len(s)
    for i in range(len(msg)):
        if msg[i:i+s_long] == s:
            str_count += 1
        if i+s_long > len(msg):
            break
    return str_count


count_content = input("请输入要统计的原内容>>：")
str_count_content = input("请输入需要统计的字符>>：")
print(count_2(count_content, str_count_content))

def count_2(msg, s):
    str_count = 0
    s_long = len(s)
    filter_position = []
    for i in range(len(msg)):
        if i in filter_position:
            continue
        if msg[i:i+s_long] == s:
            str_count += 1
            for j in range(1, s_long):
                filter_position.append(i+j)
        if i+s_long > len(msg):
            break
    return str_count


count_content = input("请输入要统计的原内容>>：")
str_count_content = input("请输入需要统计的字符>>：")
print(count_2(count_content, str_count_content))

ps：

　　方法一有bug

练习三：

选做：
xxxxxxx，请统计一下可以切割成xx多少个？用函数实现

def count_3(msg, s):
    str_count = 0
    msg_long = len(msg)
    s_long = len(s)
    i = 0
    while i < msg_long:
        if msg[i:i+s_long] == s:
            str_count += 1
            i = i+s_long
        else:
            i += 1
        if i + s_long > msg_long:
            break
    return str_count


count_content = input("请输入要统计的原内容>>：")
str_count_content = input("请输入需要统计的字符>>：")
print(count_3(count_content, str_count_content))