Python3字符串学习教程

>>> 'Let's go!' 
SyntaxError: invalid syntax 
>>> "Let's go!" 
"Let's go!" 
>>> 'Let\'s go!' 
"Let's go!" 
>>> '''''begin 
and 
next 
end''' 
'begin\nand\nnext\nend' 

>>> s = "HelloWorld" 
>>> s[0] = 'h' 
Traceback (most recent call last): 
 File "<pyshell#123>", line 1, in <module> 
  s[0] = 'h' 
TypeError: 'str' object does not support item assignment 

>>> s 
'HelloWorld' 
>>> L = list(s) 
>>> L 
['H', 'e', 'l', 'l', 'o', 'W', 'o', 'r', 'l', 'd'] 
>>> L[0] = 'h' 
>>> ''.join(L) #这是什么?别着急，下面我们会谈到 
'helloWorld' 

>>> s = "Hello""World" 
>>> s 
'HelloWorld' 
>>> s1 = "Hello" 
>>> s2 = "World" 
>>> s1s2 
Traceback (most recent call last): 
 File "<pyshell#138>", line 1, in <module> 
  s1s2 
NameError: name 's1s2' is not defined 
>>> s1+s2 
'HelloWorld' 

>>> s = "HelloWorld" 
>>> len(s) 
10 
>>> "ll" in s 
True 

>>> s 
'HelloWorld' 
>>> s.find("l") 
2 
>>> s.find('w') 
-1 

>>> s = '''''begin 
...then.. 
...next.. 
end...''' 
>>> s.splitlines() 
['begin', '...then..', '...next..', 'end...'] 

>>> s = "here#there" 
>>> s.split('#') # #作为分隔符 
['here', 'there'] 
>>> s = '''''begin 
.then.. and 
.next. 
end''' 
>>> s.split() #默认情况将所有换行和空格都分割 
['begin', '.then..', 'and', '.next.', 'end'] 

>>> s = 'HelloWorld' 
>>> s.lower() 
'helloworld' 
>>> s.upper() 
'HELLOWORLD' 

>>> L = ['1','33','42'] 
>>> '+'.join(L) #用+来连接 
'1+33+42' 
>>> L = list(s) #拆开s 
>>> L 
['H', 'e', 'l', 'l', 'o', 'W', 'o', 'r', 'l', 'd'] 
>>> ''.join(L) #粘合了。。。 
'HelloWorld' 

>>> s 
'HelloWorld' 
>>> s.replace("World","Cheng") 
'HelloCheng' 
>>> s.replace("world","Cheng") #知道为什么吧... 
'HelloWorld' 

>>> s = "  Hi,I'm Alice!  " 
>>> s.strip() 
"Hi,I'm Alice!" 
>>> s.strip("! ") #这是两个字符哦 
"Hi,I'm Alice" #少了一个感叹号哦！ 

>>> name = 'Jonh' 
>>> call = '13560300xxx' 
>>> "{0}'s telephone number is {1}".format(name,call) # (1) 
"Jonh's telephone number is 13560300xxx" 
>>> addr = "A103" 
>>> "{0}'s telephone number is {1} and his address is {2}".format(name,call,addr) #(2) 
"Jonh's telephone number is 13560300xxx and his address is A103" 

>>> L = [2,3,5,7] 
>>> print("x is {0[0]}, y is {0[2]}".format(L)) 
x is 2, y is 5 

>>> d 
{'b': 2, 'a': 1} 
>>> print("x is {0[a]}, y is {0[b]}".format(d)) 
x is 1, y is 2 
>>> d = {2:3.5,7:4.5} 
>>> print("x is {0[2]}, y is {0[7]}".format(d)) 
x is 3.5, y is 4.5 

>>> print("{0.random}".format(random)) 
<built-in method random of Random object at 0x022D61F8> 

>>> class A: 
  pass 
 
>>> x = A() 
>>> print("The class is {0.__class__}".format(x)) 
The class is <class '__main__.A'> 

>>> print("{name}'s telephone number is {call}".format(name = "Jonh",call = 69993)) 
Jonh's telephone number is 69993 

>>> pi = 3.141592653 
>>> print("The pi is {0:10.3f}".format(pi)) # 0:10.3f 表示输出宽度为10，保留三位小数，浮点数 
The pi is   3.142