var1 = 'Hello World!'
var2 = "Python Programming"

访问字符串的值

#!/usr/bin/python3

var1 = 'Hello World!'
var2 = "Python Programming"

print ("var1[0]: ", var1[0])
print ("var2[1:5]: ", var2[1:5])

var1[0]:  H
var2[1:5]:  ytho

更新字符串

可以通过(再)分配给另一个字符串变量来“更新”现有的字符串。新的值可以相关联它之前的值或使用另一个完全不同的字符串。例如 -

#!/usr/bin/python3

var1 = 'Hello World!'

print ("Updated String :- ", var1[:6] + 'Python')

Updated String :-  Hello Python

转义字符

字符串特殊操作符

字符串格式化操作

Python有一个最酷的功能是字符串格式运算符%。这个操作符对于字符串是是唯一的，并填补了 C语言中 printf()系列函数。下面是一个简单的例子-

#!/usr/bin/python3

print ("My name is %s and weight is %d kg!" % ('Zara', 21)) 

My name is Zara and weight is 21 kg!

三重引号

#!/usr/bin/python3

para_str = """this is a long string that is made up of
several lines and non-printable characters such as
TAB ( \t ) and they will show up that way when displayed.
NEWLINEs within the string, whether explicitly given like
this within the brackets [ \n ], or just a NEWLINE within
the variable assignment will also show up.
"""
print (para_str) 

当执行上面的代码，它产生了以下结果。注意，如何每一个特殊字符已经转换到它的打印形式，一直到最后的NEWLINE之间的字符串的结尾关闭三重引号。还要注意的是出现新行或者使用一行或末尾明确回车其换码(\ n)-

this is a long string that is made up of
several lines and non-printable characters such as
TAB (    ) and they will show up that way when displayed.
NEWLINEs within the string, whether explicitly given like
this within the brackets [
 ], or just a NEWLINE within
the variable assignment will also show up. 

原始字符串不会把反斜杠作为一个特殊字符。 把一个原始字符串中的每个字符保持原来编写的方式 -

#!/usr/bin/python3
(
print ('C:\\nowhere')

C:\nowhere

#!/usr/bin/python3

print (r'C:\\nowhere')

C:\\nowhere

Unicode字符串

在Python 3，所有的字符串都是以Unicode表示。在Python2中内部存储为8位ASCII，因此，它需要附上“u”以让明确使用的是Unicode。但在Python3 中现在不再是必要的。

字符串内置的方法