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Work With a Token
00:00
The regular expression for support_tom could actually look very similar. When you put in \[support_tom\], you can see that [support_tom] with the square brackets is selected in your test string. However, this is a good point where we could be a bit more flexible and actually leverage the powers of regular expressions. What if there are multiple support agents?
00:25 So you don’t want to look specifically for Tom, but basically for any support agent.
00:32
For this, you can use a so-called token, and the token that you want to use is the w. But since the w now should have a special meaning, it’s not enough to just put a w into it. Instead, you need to put the escape character (\) in front of it. Again,
00:50
once you put a backslash in front of the w, you can see regex101 marks the regular expression input string a bit different. However, the way that it’s written right now, your regular expression doesn’t find any match in the test string.
01:06
So, the next thing that you need to do is to put an asterisk (*).
01:11
What exactly happened there? With an asterisk, you say that the token that was used before should match zero or multiple times. So you look for a string that’s in square brackets and says support and any alphanumerical character. That could be a letter, a number, or the underscore. In your text below, there are always more characters before the closing square bracket, and that’s why when you add the asterisk, now the [support_tom] username in square brackets matches. And again, the cool thing is even if it would be [support_tommy], you can see that the test string is still highlighted, so your regular expression pattern still finds the username.
01:53
That’s cool. Okay, but let’s leave it with support_tom and copy the regular expression input and save it in text file because you will need it in a moment.
Bartosz Zaczyński RP Team on Jan. 20, 2025
@Ray The predefined character class \w, which is short for [_a-zA-Z0-9], matches exactly one character that belongs to the class. If you want to match more characters, then you must combine the class with a quantifier, such as + (one or more), * (zero or more), or {n:m} (between n and m characters). A quantifier always applies to the element before it.
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Ray on Jan. 19, 2025
Why couldn’t the expression
r"\[support\w\]find any matches without the'*'?