python - 我怎样才能在 python 中获得重新模式作为动态输入？

Question

我在 python 中使用 re 模块进行一些正则表达式操作。当我在 python 程序中定义要静态匹配的模式时，它工作正常。

例如，

import re
s="hi can you help me out"
pattern=r'[a-z ]*' #pattern that takes space and lower case letters only
i= re.fullmatch(pattern,s) #to check the entire string
print(i.string)


output:
hi can you help me out

现在让我来谈谈我遇到的问题是，如果我试图在运行时从用户那里获取输入模式，它会抛出异常。这里是代码

import re
s="hi can you help me out"
pattern=input("Enter pattern:")
i= re.fullmatch(pattern,s)
print(i.string)

output:
Enter pattern:r'[a-z]*'
Exception has occurred: AttributeError
'NoneType' object has no attribute 'string'

希望有人帮我解决这个问题。

python 版本:3.5

提前致谢

Answer 1

你只需要输入这部分 [a-z ]* 没有 r 字符串前缀:

Python 3.x:

import re
s = "hi can you help me out"
pattern = input("Enter pattern:")
i = re.fullmatch(pattern,s)
print(i.string)

Python 2.x:

import re
s = "hi can you help me out"
pattern = raw_input("Enter pattern:")   # since input() in python2.x is the same eval(raw_input()) which would return an int
i = re.fullmatch(pattern,s)
print(i.string)

输出:

Enter pattern:[a-z ]*
hi can you help me out