python 正确字符串处理

不管是谁，只要处理过由用户提交的调查数据，就能明白这种乱七八糟的数据是怎么一回事。为了得到一组能用于分析工作的格式统一的字符串，需要做很多事情：去除空白符、删除各种标点符号、正确的大写格式等。做法之一是使用内建的字符串方法和正则表达式re模块：

一般写法

states = ['   Alabama ', 'Georgia!', 'Georgia', 'georgia', 'FlOrIda',
         'south   carolina##', 'West virginia?']

import re

def clean_strings(strings):  # 一般对数据的处理步骤
    result = []
    for value in strings:
        value = value.strip()
        value = re.sub('[!#?]', '', value)
        value = value.title()
        result.append(value)
    return result

In [173]: clean_strings(states)
Out[173]: 
['Alabama',
 'Georgia',
 'Georgia',
 'Georgia',
 'Florida',
 'South   Carolina',
 'West Virginia']

推荐写法

这种多函数模式使你能在很高的层次上轻松修改字符串的转换方式。此时的clean_strings也更具可复用性！

def remove_punctuation(value):
    return re.sub('[!#?]', '', value)

clean_ops = [str.strip, remove_punctuation, str.title]  # 函数也是对象

def clean_strings(strings, ops):
    result = []
    for value in strings:
        for function in ops:
            value = function(value)
        result.append(value)
    return result

In [175]: clean_strings(states, clean_ops)
Out[175]: 
['Alabama',
 'Georgia',
 'Georgia',
 'Georgia',
 'Florida',
 'South   Carolina',
 'West Virginia']

# 或者
In [176]: for x in map(remove_punctuation, states):  #  
   .....:     print(x)
Alabama 
Georgia
Georgia
georgia
FlOrIda
south   carolina
West virginia