Need regular expression expert: round bracket within stringliteral...

Question

I'm searching for strings within strings using Regex. The pattern is a string literal that ends in (, e.g.

# pattern
" before the bracket ("

# string
this text is before the bracket (and this text is inside) and this text is after the bracket

I know the pattern will work if I escape the character with a backslash, i.e.:

# pattern
" before the bracket \\("

But the pattern strings are coming from another search and I can not control what characters will be or where. Is there a way of escaping an entire string literal so that anything between markers is treated as a string? For example:

# pattern
\" before the ("

The only other option I have is to do a substitute adding escapes for every protected character.

Answer 1

The following regex will capture everything from the beginning of the string to the first (. The first captured group $1 will contain the portion before (.

^([^(]+)\(

Depending on your language, you might have to escape it as:

"^([^(]+)\\("

Answer 2

You didn't specify the language, but it looks like Python, so if you have a string in Python whose special regex characters you need to escape, use re.escape():

>>> import re
>>> re.escape("Wow. This (really) is *cool*")
'Wow\\.\\ This\\ \\(really\\)\\ is\\ \\*cool\\*'

Note that spaces are escaped, too (probably to ensure that they still work in a re.VERBOSE regex).

Answer 3

Hi Tim,

re.escape is exactly what I need. I'm using regexp in Access VBA which doens't have that method. I only have replace, execute or test methods.

Is there a way to escape everything within a string in VBA?

Thanks

Answer 4

Maybe write your own VBA escape function:

Function EscapeRegEx(text As String) As String
    Dim regEx As RegExp
    Set regEx = New RegExp

    regEx.Global = True
    regEx.Pattern = "(\[|\\|\^|\$|\.|\||\?|\*|\+|\(|\)|\{|\})"

    EscapeRegEx = regEx.Replace(text, "\$1")
End Function

Answer 5

I'm pretty sure that with the limitations of the RegExp abilities in VBA/VBScript, you are going to have to replace the special characters in your pattern before using it. There doesn't seem to be anything built into it like there is in Python.