CODEWITHSUNDEEP
pythonregex
Pedram
Pedram

Reputation: 2611

Updating a string using regular expressions in Python

I'm pretty sure that my question is very straightforward but I cannot find the answer to it. Let's say we have an input string like:

input = "This is an example"

Now, I want to simply replace every word --generally speaking, every substring using a regular expression, "word" here is just an example-- in the input with another string which includes the original string too. For instance, I want to add an @ to the left and right of every word in input. And, the output would be:

output = "@This@ @is@ @an@ @example@"

What is the solution? I know how to use re.sub or replace, but I do not know how I can use them in a way that I can update the original matched strings and not completely replace them with something else.

Upvotes: 0

Views: 860

Answers (4)

iz_
iz_

Reputation: 16583

You can match only word boundaries with \b:

import re

input = "This is an example"
output = re.sub(r'\b', '@', input)
print(output)


@This@ @is@ @an@ @example@

Upvotes: 0

fulaphex
fulaphex

Reputation: 3219

You can use capture groups for that. 

import re

input = "This is an example"
output = re.sub("(\w+)", "@\\1@", input)

A capture group is something that you can later reference, for example in the substitution string. In this case, I'm matching a word, putting it into a capture group and then replacing it with the same word, but with @ added as a prefix and a suffix.

You can read about regexps in python more in the docs.

Upvotes: 1

Tim Biegeleisen
Tim Biegeleisen

Reputation: 520978

Here is an option using re.sub with lookarounds:

input = "This is an example"
output = re.sub(r'(?<!\w)(?=\w)|(?<=\w)(?!\w)', '@', input)

print(output)

@This@ @is@ @an@ @example@

Upvotes: 1

Kartikeya Sharma
Kartikeya Sharma

Reputation: 1383

This is without re library

a = "This is an example"
l=[]
for i in a.split(" "):
    l.append('@'+i+'@')

print(" ".join(l))

Upvotes: 0

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