regular expression to match pattern in string

Question

Below is the sample words that I will use at time of file import

East Chesterton (Cambridge)
New york (USA)
child (parent)

So here are the business rules:

First word should be at least 3 chars long (l.e child)
Allow space , but it's invalid if there's only space (l.e East Chesterton)
The other part of the word is in ( someword )
The ( someword ) is optional
If ( someword ) is there it's minimum length is of 3, and spaces are also allowed.

I have achieved this at some level using following expression:

^[a-zA-Z ]{1,}\([a-zA-Z ]{1,}\)$

Now i want to make sure this is correct expression. Is there any way to check with automation to check multiple combination to verify my expression?
How i can achieve optional part (point no. 4), It min whether i pass (somedata) or not that check for first part.

Also to extract data in '( )'

\((.*?)\)

{1,} matches a single occurrence or more, but you said you need at least 3 characters, so that should be {3,}. For optional parts, use ?. Note that (...) indicates a group. To match parentheses, you need to escape them: $ and $. Also note that you can use character classes such as \w (word characters) and \s (whitespace characters) instead of explicit ranges. You can also allow (optional) whitespace in-between the first and the second part with \s* (0 or more whitespace characters). — Pieter Witvoet
– Pieter Witvoet, Commented Dec 31, 2015 at 13:34
Although you can use regex101 for this task, mind that that site does not support .NET regex syntax. Use regexhero.net or regexstorm.net. Now, your requirements are not that clear: what is the min. length of 3? The first word or all the subparts? To test the regex, you should think of possible input string types yourself, there is no way to create test strings automatically. Content drives regex, not vice versa. Try this regex: ^(?=[a-z]{3,})[a-z ]+(?:\p{Zs}$(?=[a-z]{3,})[a-z ]+$)?\r?$ — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 31, 2015 at 13:48
One change to @stribizhev 's regex: the requirement is to have minimum length of 3 (in two places). (?=[a-z]{3,}) does that, but it is also followed up with [a-z ]+, effectively making it a minimum of 4. The second should use * instead of +. — EvilBob22
– EvilBob22, Commented Dec 31, 2015 at 15:59

Marnix · Accepted Answer · 2015-12-31 13:33:08Z

2

I think you are almost there. I did a try. Does this comply to all your requirements?

^[a-zA-Z\s]{3,}(\([a-zA-Z\s]{3,}\))?$

https://regex101.com/r/yE9lB0/2

I made the second part optional by putting it in between parenthesis and adding a question mark at the end: (myoptionalexpression)?

answered Dec 31, 2015 at 13:33

Marnix

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Work of Artiz · Accepted Answer · 2015-12-31 15:19:37Z

I've taken a look at the answer posted here.

 ^[a-zA-Z\s]{3,}(\([a-zA-Z\s]{3,}\))?$

This would clash with

Allow space , but it's invalid if there's only space (l.i East Chesterton)

Only empty spaces would already match.

Besides that the description 'characters' might be a bit vague. I have therefore assumed word characters \w are what you mean. (in C sharp \w should include unicode characters like ü as well. Think of Münster (Germany) as example.

The new regex would look like this:

^\s*(?:\w{3,}\s*)+(?:\(\s*(?:\w{3,}\s*)+\))?\s*$

Examples here: https://regex101.com/r/gS7kG8/3

Note that the regex101 page works with php,python and js regex, it will not give exact results in case of C# (\w in php apparently doesn't match unicode for instance)

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