python标准库介绍——23 UserString 模块详解

==UserString 模块==


(2.0 新增) ``UserString`` 模块包含两个类, //UserString// 和 //MutableString// . 
前者是对标准字符串类型的封装, 后者是一个变种, 允许你修改特定位置的字符(联想下列表就知道了).

注意 //MutableString// 并不是效率很好, 许多操作是通过切片和字符串连接实现的. 如果性能很对你的脚本来说重要的话, 你最好使用字符串片断的列表或者 ``array`` 模块. 
[Example 2-17 #eg-2-17] 展示了 ``UserString`` 模块.

====Example 2-17. 使用 UserString 模块====[eg-2-17]

```
File: userstring-example-1.py

import UserString

class MyString(UserString.MutableString):

    def append(self, s):
        self.data = self.data + s

    def insert(self, index, s):
        self.data = self.data[index:] + s + self.data[index:]

    def remove(self, s):
        self.data = self.data.replace(s, "")

file = open("samples/book.txt")
text = file.read()
file.close()

book = MyString(text)

for bird in ["gannet", "robin", "nuthatch"]:
    book.remove(bird)

print book

*B*...
C: The one without the !
P: The one without the -!!! They've ALL got the !! It's a
Standard British Bird, the , it's in all the books!!!
...*b*
```