General question, escape square brackets in string while using boundaries

General Discussion
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1

I'm struggling to find a solution, I'm trying to make a simple app in Perspective that can take FactoryTrash ME window exports and do a search and replace. I have a lookup table that is the current address and what the new address should be.

Here is a short example:

import re

oldAddress = "::[PLC]N22:21"
newAddress = "[PLC]N22[21]"
data = '<connection name="Value" expression="{::[PLC]N22:211} * .1"/>'
data = data.replace(oldAddress, newAddress)
print data

Result:

<connection name="Value" expression="{[PLC]N22[21]1} * .1"/>

The issue is it should be:

<connection name="Value" expression="{[PLC]N22[21]} * .1"/>

When I want to match whole word boundaries I will use this:

data = re.sub(r"\b%s\b" % re.escape(oldAddress), newAddress, data)

However, this doesn't work with square brackets in the string.

How can I escape square brackets and still search with boundaries?

2

To have regex see square brackets, you have to escape them with \.
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However, help me understand. Your oldAddress ends with 21, not 211, so it would not replace the last 1 in the data string because its not part of the searched string. Don't you want your oldAddress to be ::[PLC]N22:211?

1 Like
3

I tried escaping with backslashes and I couldn't get it to work, but perhaps I was overlooking something.

In my example, nothing should have been replaced, {::[PLC]N22:211} should have remained as-is. My point was using replace would still replace the text, which is why I wanted to use boundaries.

I'll be honest, this app is really simple and it's just something I want to use for conversion projects. So, not important, IMO, to be best practice, so for right now I just added back in the curly brackets, then do the replace. I should have mentioned this is replacing direct tags which are always wrapped in curly brackets and will include a shortcut (the stuff with square brackets).

4

I found some of the online regex generators useful. e.g.

2 Likes
5

You can end your regex expression with (?=}) to specify that is should be followed by a curly brace but not included. This is a positive lookahead.

Not matching:
image

Matching:
image

1 Like