regular expression generation

I have a regular expression

"[a-z][0-9][a-z][0-9][a-z][0-9]"

From this i want to generate a regular expression exclude the characters D, F, I, O, Q and U. That is "Q3D4R5" 开发者_运维知识库should not be included.

How should i do this?

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Just use a negative lookahead to exclude those characters from your string.

(?!.*[DFIOQU])(?:[a-z][0-9]){3}

http://www.rubular.com

Some explanations:

(?!.*[DFIOQU]) checks the complete string if there is a occurrence of a character from the character group, if so then the whole thing is False.

(?:)defines a non capturing group that is repeated 3 times {3}.

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Your regex matches only lowercase characters, so I assume you want to exclude d, f, i, o, q and u .

You can rewrite your original regex as

   ([a-z][0-9]){3} 

This regex you can modify to

([a-ceghj-nprstv-z][0-9]){3}  

to achieve what you want

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You can use

[a-ceghj-nprsv-z]

instead of

[a-z]

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if case matters then to filter the letters part:

[a-zA-CEGHJ-NPRSV-Z]

this will allow any lower case letter but not the upper case ones specified.

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as suggested in other answers, you can include specific characters as well as more specific ranges in suare brackets; assuming your regexp matching is not case-sensitive (otherwise your original example presumably wouldn't be working), you could have:

"[a-ceghj-nprsv-z][0-9][a-ceghj-nprsv-z][0-9][a-ceghj-nprsv-z][0-9]"

Now if you also want to validate length (if there's any possibility that you had a value like "A1A1A1A", and you did NOT want that to match), then you'd also need to detect the start and end of the expression, eg:

"^[a-ceghj-nprsv-z][0-9][a-ceghj-nprsv-z][0-9][a-ceghj-nprsv-z][0-9]$"

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I checked the following two cases at http://tools.netshiftmedia.com/regexlibrary/ and they appear to work.

^(?!.D.)^(?!.F.)^(?!.I.)^(?!.O.)^(?!.Q.)^(?!.U.)[a-z][0-9][a-z][0-9][a-z][0-9]

[a-ce-ghj-npr-tv-z][0-9][a-ce-ghj-npr-tv-z][0-9][a-ce-ghj-npr-tv-z][0-9]

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I have found this "regular expression editor" web site: http://www.rubular.com/
very useful.