Remove words of length less than 4 from string [duplicate]

Question

I am trying to remove words of length less than 4 from a string.

I use this regex:

 re.sub(' \w{1,3} ', ' ', c)

Though this removes some strings but it fails when 2-3 words of length less than 4 appear together. Like:

 I am in a bank.

It gives me:

 I in bank. 

How to resolve this?

Answer 1

Don't include the spaces; use \b word boundary anchors instead:

re.sub(r'\b\w{1,3}\b', '', c)

This removes words of up to 3 characters entirely:

>>> import re
>>> re.sub(r'\b\w{1,3}\b', '', 'The quick brown fox jumps over the lazy dog')
' quick brown  jumps over  lazy '
>>> re.sub(r'\b\w{1,3}\b', '', 'I am in a bank.')
'    bank.'

Answer 2

If you want an alternative to regex:

new_string = ' '.join([w for w in old_string.split() if len(w)>3])

Answer 3

Answered by Martijn, but I just wanted to explain why your regex doesn't work. The regex string ' \w{1,3} ' matches a space, followed by 1-3 word characters, followed by another space. The I doesn't get matched because it doesn't have a space in front of it. The am gets replaced, and then the regex engine starts at the next non-matched character: the i in in. It doesn't see the space before in, since it was placed there by the substitution. So, the next match it finds is a, which produces your output string.