Python Regular Expression example

Question

I want to write a simple regular expression in Python that extracts a number from HTML. The HTML sample is as follows:

Your number is 123
         


        

Answer 1

val="Your number is <b>123</b>"

Option : 1

m=re.search(r'(<.*?>)(\d+)(<.*?>)',val)

m.group(2)

Option : 2

re.sub(r'([\s\S]+)(<.*?>)(\d+)(<.*?>)',r'\3',val)

Answer 2

Given s = "Your number is <b>123</b>" then:

 import re 
 m = re.search(r"\d+", s)

will work and give you

 m.group()
'123'

The regular expression looks for 1 or more consecutive digits in your string.

Note that in this specific case we knew that there would be a numeric sequence, otherwise you would have to test the return value of re.search() to make sure that m contained a valid reference, otherwise m.group() would result in a AttributeError: exception.

Of course if you are going to process a lot of HTML you want to take a serious look at BeautifulSoup - it's meant for that and much more. The whole idea with BeautifulSoup is to avoid "manual" parsing using string ops or regular expressions.

Answer 3

The simplest way is just extract digit(number)

re.search(r"\d+",text)