How to match entire words dynamically using Regex in Python

Question

Using Regex, I want to match a sequence of words entirely in Python. Statically it is possible, but I am unaware about the dynamic way of matching.

Static method

import re
print(re.search(r'\bsmaller than or equal\b', 'When the loan amount is smaller than or equal to 50000'))

I am trying to do the same thing dynamically, by matching the entire sequence with a list.
Here is the code snippet below:

import re
list_less_than_or_equal = ['less than or equal', 'lesser than or equal', 'lower than or equal', 'smaller than or equal','less than or equals', 'lesser than or equals', 'lower than or equals', 'smaller than or equals', 'less than equal', 'lesser than equal', 'higher than equal','less than equals', 'lesser than equals', 'higher than equals']

for word in list_less_than_or_equal:
    print(re.search(r'\b'+word+'\b', 'When the loan amount is smaller than or equal to 50000'))

It prints None as the output.

How to match the entire sequence of words dynamically?

kennytm · Accepted Answer · 2017-05-30T07:10:15.383

6

You forgot an r in your second '\b'.

re.search(r'\b' + re.escape(word) + r'\b', ...)
#                                   ^

The escape sequence \b has special meaning in Python and will become \x08 (U+0008). The regex engine seeing \x08 will try to match this literal character and fail.

Also, I used re.escape(word) to escape special regex characters, so e.g. if a word is "etc. and more" the dot will be matched literally, instead of matching any character.

edited May 30 '17 at 07:10

answered May 30 '17 at 07:01

kennytm

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Your methodology is right, but re.quote gives an attribute error. – User456898 May 30 '17 at 07:04
1

Sorry, should be `re.escape`. Updated. – kennytm May 30 '17 at 07:05
It's proper now. – User456898 May 30 '17 at 07:09

score 2 · Answer 2 · answered May 30 '17 at 07:01

2

Instead of using concatenation, you can format your string.

re.search(r'\b{0}\b'.format(word), ....)

answered May 30 '17 at 07:01

Lafexlos

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Your method works fine. – User456898 May 30 '17 at 07:08

almost a beginner · Answer 3 · 2017-05-30T07:10:43.540

If alternative methods are options, you could compare list with list:

list_less_than_or_equal = ['less than or equal', 'lesser than or equal', 'lower than or equal', 'smaller than or equal','less than or equals', 'lesser than or equals', 'lower than or equals', 'smaller than or equals', 'less than equal', 'lesser than equal', 'higher than equal','less than equals', 'lesser than equals', 'higher than equals']

if any(word in 'When the loan amount is smaller than or equal to 50000' for word in list_less_than_or_equal):
  print("yep");
else:
  print("nope");

Or regex:

import re

list_less_than_or_equal = ['less than or equal', 'lesser than or equal', 'lower than or equal', 'smaller than or equal','less than or equals', 'lesser than or equals', 'lower than or equals', 'smaller than or equals', 'less than equal', 'lesser than equal', 'higher than equal','less than equals', 'lesser than equals', 'higher than equals']

if any(re.findall(r'|'.join(list_less_than_or_equal), 'When the loan amount is smaller than or equal to 50000', re.IGNORECASE)):
    print ('yep')
else:
    print ('nope')

Your answer is very good, but unfortunately only 1 answer can be chosen for the tick mark. — User456898, May 30 '17 at 07:12

How to match entire words dynamically using Regex in Python

3 Answers3