Python进行文本处理

对于一个文本字符串，可以使用Python的string.split()方法将其切割。下面看看实际运行效果。

mySent = ‘This book is the best book on python!‘
print mySent.split()

输出：

[‘This‘, ‘book‘, ‘is‘, ‘the‘, ‘best‘, ‘book‘, ‘on‘, ‘python!‘]

可以看到，切分的效果不错，但是标点符号也被当成了词，可以使用正则表达式来处理，其中分隔符是除单词、数字外的任意字符串。

import re
reg = re.compile(‘\\W*‘)
mySent = ‘This book is the best book on python!‘
listof = reg.split(mySent)
print listof

输出为：

[‘This‘, ‘book‘, ‘is‘, ‘the‘, ‘best‘, ‘book‘, ‘on‘, ‘python‘, ‘‘]

现在得到了一系列词组成的词表，但是里面的空字符串需要去掉。

可以计算每个字符串的长度，只返回大于0的字符串。

import re
reg = re.compile(‘\\W*‘)
mySent = ‘This book is the best book on python!‘
listof = reg.split(mySent)
new_list = [tok for tok in listof if len(tok)>0]
print new_list

输出为：

[‘This‘, ‘book‘, ‘is‘, ‘the‘, ‘best‘, ‘book‘, ‘on‘, ‘python‘]

最后，发现句子中的第一个字母是大写的。我们需要同一形式，把大写转化为小写。Python内嵌的方法，可以将字符串全部转化为小写（.lower（））或大写(.upper())

import re
reg = re.compile(‘\\W*‘)
mySent = ‘This book is the best book on python!‘
listof = reg.split(mySent)
new_list = [tok.lower() for tok in listof if len(tok)>0]
print new_list

输出为：

[‘this‘, ‘book‘, ‘is‘, ‘the‘, ‘best‘, ‘book‘, ‘on‘, ‘python‘]

下面来看一封完整的电子邮件：

内容

Hi Peter,

With Jose out of town, do you want tomeet once in a while to keep thingsgoing and do some interesting stuff?

Let me knowEugene

import re
reg = re.compile(‘\\W*‘)
email = open(‘email.txt‘).read()
list = reg.split(email)
new_txt = [tok.lower() for tok in list if len(tok)>0]
print new_txt

输出：

[‘hi‘, ‘peter‘, ‘with‘, ‘jose‘, ‘out‘, ‘of‘, ‘town‘, ‘do‘, ‘you‘, ‘want‘, ‘to‘, ‘meet‘, ‘once‘, ‘in‘, ‘a‘, ‘while‘, ‘to‘, ‘keep‘, ‘things‘, ‘going‘, ‘and‘, ‘do‘, ‘some‘, ‘interesting‘, ‘stuff‘, ‘let‘, ‘me‘, ‘know‘, ‘eugene‘]