11.python内置数据--字符串

 1 >>> a = ‘ab‘ + ‘c‘+ ‘d‘
 2 >>> type(a)
 3 <class ‘str‘>
 4 >>> id(a)
 5 12128640
 6 >>> a = ‘ab‘ + ‘c‘+ ‘d‘+ ‘e‘
 7 >>> id(a)
 8 12128672
 9 # 内存分配的空间不一样
10 >>> a
11 ‘abcde‘
12 >>> a[1]
13 ‘b‘
14 >>> a[1] = l
15 Traceback (most recent call last):
16   File "<stdin>", line 1, in <module>
17 NameError: name ‘l‘ is not defined
18 # 和列表一样的用法，也是不可改变

 1 s1 = ‘string‘
 2 print(s1)
 3 string
 4 ##############################
 5 s2 = "string2"
 6 print(s2)
 7 string2
 8 ##############################
 9 s3 = ‘‘‘this‘s a "String"‘‘‘
10 print(s3)
11 this‘s a "String"
12 ##############################
13 s4 = ‘hello \n magedu.com‘
14 print(s4)
15 hello 
16  magedu.com
17 ##############################
18 s5 = r"hello \n magedu.com"
19 print(s5)
20 hello \n magedu.com
21 ##############################
22 s6 = ‘c:\windows\nt‘
23 print(s6)
24 c:\windows
25 t
26 ##############################
27 s7 = R"c:\windows\nt"
28 print(s7)
29 c:\windows\nt
30 ##############################
31 s8 = ‘c:\windows\\nt‘
32 print(s8)
33 c:\windows\nt
34 ##############################
35 sql = """select * from user where name=‘tom‘"""
36 print(sql)
37 select * from user where name=‘tom‘
38 
39 # 注意各种标点和转义符

 1 sql = """select * from user where name=‘tom‘"""
 2 print(sql[4])
 3 sql[4] = ‘o‘
 4 print(sql[4])
 5 #######################################
 6 c
 7 # 这里返回的是字符串‘c‘，而不是字符c
 8     sql[4] = ‘o‘
 9 TypeError: ‘str‘ object does not support item assignment
10 # 这里注意不可进行修改

1 sql = """select * from user where name=‘tom‘"""
2 for c in sql:
3     print(c,end=‘ ‘)
4 print()
5 print(type(c))
6 #####################################
7 s e l e c t   *   f r o m   u s e r   w h e r e   n a m e = ‘ t o m ‘ 
8 <class ‘str‘>

1 sql = """select * from user where name=‘tom‘"""
2 lst = list(sql)
3 print(lst)
4 t = tuple(sql)
5 print(t)
6 #######################################
7 [‘s‘, ‘e‘, ‘l‘, ‘e‘, ‘c‘, ‘t‘, ‘ ‘, ‘*‘, ‘ ‘, ‘f‘, ‘r‘, ‘o‘, ‘m‘, ‘ ‘, ‘u‘, ‘s‘, ‘e‘, ‘r‘, ‘ ‘, ‘w‘, ‘h‘, ‘e‘, ‘r‘, ‘e‘, ‘ ‘, ‘n‘, ‘a‘, ‘m‘, ‘e‘, ‘=‘, "‘", ‘t‘, ‘o‘, ‘m‘, "‘"]
8 (‘s‘, ‘e‘, ‘l‘, ‘e‘, ‘c‘, ‘t‘, ‘ ‘, ‘*‘, ‘ ‘, ‘f‘, ‘r‘, ‘o‘, ‘m‘, ‘ ‘, ‘u‘, ‘s‘, ‘e‘, ‘r‘, ‘ ‘, ‘w‘, ‘h‘, ‘e‘, ‘r‘, ‘e‘, ‘ ‘, ‘n‘, ‘a‘, ‘m‘, ‘e‘, ‘=‘, "‘", ‘t‘, ‘o‘, ‘m‘, "‘")

 1 a = ‘abcd‘
 2 b = ‘ ‘.join(a)
 3 print(b)
 4 a b c d
 5 ###################
 6 c = "@".join(a)
 7 print(c)
 8 a@b@c@d
 9 ###################
10 lst = [‘1‘,‘2‘,‘3‘]
11 print(‘ ‘.join(lst))
12 1 2 3
13 ###################
14 print("\n".join(lst))
15 1
16 2
17 3
18 ###################
19 lst1 = [‘1‘,[‘a‘,‘b‘],‘3‘]
20 print(‘ ‘.join(lst1))
21 Traceback (most recent call last):
22   File "D:/untitled/project2/day1/zifuchuan.py", line 2, in <module>
23     print(‘ ‘.join(lst1))
24 TypeError: sequence item 1: expected str instance, list foun
25 # 这种嵌套类型的会报错

 1 >>> s1 = "I‘m \ta super student."
 2 
 3 >>> s1.split()
 4 ["I‘m", ‘a‘, ‘super‘, ‘student.‘]
 5 
 6 >>> s1.split(‘s‘)
 7 ["I‘m \ta ", ‘uper ‘, ‘tudent.‘]
 8 
 9 >>> s1.split(‘super‘)
10 ["I‘m \ta ", ‘ student.‘]
11 
12 >>> s1.split(‘ ‘)
13 ["I‘m", ‘\ta‘, ‘super‘, ‘student.‘]
14 
15 >>> s1.split(‘ ‘,2)
16 ["I‘m", ‘\ta‘, ‘super student.‘]
17 
18 >>> s1.split(‘\t‘,2)
19 ["I‘m ", ‘a super student.‘]

 1 >>> ‘ab c\n\nde fg\rk|\r\n‘.splitlines()
 2 [‘ab c‘, ‘‘, ‘de fg‘, ‘k|‘]
 3 # 行分隔符包括\n、\r\n、\r等等
 4 
 5 >>> ‘ab c\n\nde fg\rk|\r\n‘.splitlines(True)
 6 [‘ab c\n‘, ‘\n‘, ‘de fg\r‘, ‘k|\r\n‘]
 7 #True保留行分隔符
 8 
 9 >>> s1 = ‘‘‘I‘m a super student.You‘re a super teacher.‘‘‘
10 >>> print(s1)
11 I‘m a super student.You‘re a super teacher.
12 
13 >>> print(s1.splitlines())
14 ["I‘m a super student.You‘re a super teacher."]
15 
16 >>> print(s1.splitlines(True))
17 ["I‘m a super student.You‘re a super teacher."]

 1 >>> s1 = "I‘m a super student."
 2 >>> s1.partition(‘s‘)
 3 ("I‘m a ", ‘s‘, ‘uper student.‘)
 4 
 5 >>> s1.partition(‘stu‘)
 6 ("I‘m a super ", ‘stu‘, ‘dent.‘)
 7 
 8 >>> s1.partition(‘‘)
 9 Traceback (most recent call last):
10   File "<stdin>", line 1, in <module>
11 ValueError: empty separator
12 # 分隔符不能为空 
13 
14 >>> s1.partition(‘ ‘)
15 ("I‘m", ‘ ‘, ‘a super student.‘)
16 
17 >>> s1.partition(‘abc‘)
18 ("I‘m a super student.", ‘‘, ‘‘)

1 >>> s1 = "I‘m a super student."
2 >>> s1.upper()
3 "I‘M A SUPER STUDENT."
4 
5 >>> s1.lower()
6 "i‘m a super student."
7 
8 >>> s1.swapcase()
9 "i‘M A SUPER STUDENT."

 1 >>> s = "I‘m a super STUDENT."
 2 >>> s.title()
 3 "I‘M A Super Student."
 4 
 5 >>> s.capitalize()
 6 "I‘m a super student."
 7 
 8 >>> s.center(20)
 9 "I‘m a super STUDENT."
10 
11 >>> s.center(50)
12 "               I‘m a super STUDENT.               "
13 
14 >>> s.center(50,‘#‘)
15 "###############I‘m a super STUDENT.###############"
16 
17 >>> s.zfill(50)
18 "000000000000000000000000000000I‘m a super STUDENT."
19 
20 >>> s.ljust(50,‘#‘)
21 "I‘m a super STUDENT.##############################"
22 
23 >>> s.rjust(50,‘#‘)
24 "##############################I‘m a super STUDENT."

 1 >>> ‘www..magedu.com‘.replace(‘w‘,‘p‘)
 2 ‘ppp..magedu.com‘
 3 
 4 >>> ‘www..magedu.com‘.replace(‘w‘,‘p‘,2)
 5 ‘ppw..magedu.com‘
 6 
 7 >>> ‘www..magedu.com‘.replace(‘w‘,‘p‘,1)
 8 ‘pww..magedu.com‘
 9 
10 >>> ‘www..magedu.com‘.replace(‘ww‘,‘p‘,2)
11 ‘pw..magedu.com‘
12 
13 >>> ‘www..magedu.com‘.replace(‘www‘,‘python‘,2)
14 ‘python..magedu.com‘

 1 >>> s = "\r \n \t Hello Python \n \t"
 2 >>> s.strip()
 3 ‘Hello Python‘
 4 # 默认去掉两端的空白字符
 5 
 6 >>> s1 = " I am very very very sorry    "
 7 >>> s1.strip()
 8 ‘I am very very very sorry‘
 9 
10 >>> s1.strip(‘r‘)
11 ‘ I am very very very sorry    ‘
12 # 因为首尾两端都没有r，因此无修改
13 
14 >>> s1.strip(‘r y‘)
15 ‘I am very very very so‘
16 # 这里要注意，去除的是r、空格和y这三个字符，首端查找有空格去掉，尾端先去掉空格，再去掉字符y，再去掉两个字符r
17 
18 >>> s1.strip(‘r yIamso‘)
19 ‘very very ve‘
20 
21 >>> s1.lstrip(‘r yIamso‘)
22 ‘very very very sorry    ‘
23 
24 >>> s1.rstrip(‘r yIamso‘)
25 ‘ I am very very ve‘
26 >>>

 1 >>> s = "I am very very very sorry"
 2 >>> s.find(‘very‘)
 3 5
 4 # 每一个字母每一个空格都算一个字符
 5 # 且从0开始算起，I+空格+a+m+空格，正好第6个是very，因此返回5
 6 >>> s.find(‘very‘,5)
 7 5
 8 # 表示是从第5个开始查
 9 >>> s.find(‘very‘,6,13)
10 -1
11 # 表示是从第6个开始查，到第13个结束，查询不到返回-1的结果
12 >>> info = ‘abca‘
13 >>> info.find(‘a‘)
14 0
15 # 从下标0开始，查找在字符串里第一个出现的子串，返回结果0
16 >>> info.find(‘a‘,1)
17 3
18 # 从下标1开始，查找在字符串里第一个出现的子串：返回结果3
19 >>> info.find(‘3‘)
20 -1
21 # 查找不到返回-1

 1 >>> a = "I am very very very sorry"
 2 >>> a.index(‘very‘)
 3 5
 4 >>> a.index(‘very‘,5)
 5 5
 6 >>> a.index(‘very‘,6,13)
 7 Traceback (most recent call last):
 8   File "<stdin>", line 1, in <module>
 9 ValueError: substring not found
10 >>> a.rindex(‘very‘,10)
11 15
12 >>> a.rindex(‘very‘,10,15)
13 10
14 >>> a.rindex(‘very‘,-10,-1)
15 15
16 # 注意与find()比较

 1 >>> a = "I am very very very sorry"
 2 >>> a.rindex(‘very‘,10)
 3 15
 4 >>> a.rindex(‘very‘,10,15)
 5 10
 6 >>> a.rindex(‘very‘,-10,-1)
 7 15
 8 >>> a.count(‘very‘)
 9 3
10 >>> a.count(‘very‘,5)
11 3
12 >>> a.count(‘very‘,10,14)
13 1
14 # 注意，count是统计个数的

 1 >>> a = "I am very very very sorry"
 2 >>> a.startswith(‘very‘)
 3 False
 4 >>> a.startswith(‘very‘,5)
 5 True
 6 >>> a.startswith(‘very‘,5,9)
 7 True
 8 >>> a.endswith(‘very‘,5,9)
 9 True
10 >>> a.endswith(‘very‘,5)
11 False
12 >>> a.endswith(‘very‘,5,-1)
13 False
14 >>> a.endswith(‘very‘,5,100)
15 False
16 >>> a.endswith(‘sorry‘,5)
17 True
18 >>> a.endswith(‘sorry‘,5,-1)
19 False
20 >>> a.endswith(‘sorry‘,5,100)
21 True
22 # 注意左闭右开，5,9是从第5个字串开始到第8个字串，不含第9个