Regex - delete numbers from string [closed]

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I'd like to find a regex expression to remove numbers from string Only if the char before any number is not alphabetic or is a whitespace. For instance:

_123
(1234
.12345
?!8
hi 123
?? 1234

will be

_
(
.
?!
hi
??

on the other hand:

aaa123
A1234
Z_L12345
..A8
aaa a123

will be:

aaa123
A1234
Z_L12345
..A8
aaa a123

Any ideas?

Thank you!

@vks I thought the language was not necessary, I'm using PHP. Edited. — Frank
– Frank, Commented Oct 18, 2014 at 7:31
char before any number is not alphabetic then how come A1234 became A? — anubhava
– anubhava, Commented Oct 18, 2014 at 7:33
Refer stackoverflow.com/questions/3363005/… stackoverflow.com/questions/7847223/… — user4094161
– user4094161, Commented Oct 18, 2014 at 7:34

vks · Accepted Answer · 2014-10-18 08:29:55Z

1

[ ]\d+|(?<=[^a-zA-Z0-9\n])\d+

Try this.Replace with empty string.See demo.

http://regex101.com/r/mE6hO4/5

edited Oct 18, 2014 at 8:29

answered Oct 18, 2014 at 7:38

vks

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1 Comment

Frank Over a year ago

Thanks. I forgot to add this: 123 hi will remain 123 hi, how can I do that too?

Mehdi Khademloo · Accepted Answer · 2014-10-18 08:08:13Z

1

use the lookbehind assertion for this, for example for your case use look behind for behind of your match case, it can't be "A-Z" or "a-z" or "0-9" then you should create a set from these and insert it to look-behind.

this is your regex

(?<=[^a-zA-Z0-9])\d+

and this is your demo

http://regex101.com/r/dN8sA5/21

then you should replace it with NULL string.

Edit: it's very better to Trim your final string with one of these approach

Use Regex: \s*(?<=[^a-zA-Z0-9])\d+\s*
Use Trim: after the replacing your string, use String.Trim for removing arounding space with the string.

I really prefer the first approach...

for more information about look-behind see this:

http://www.regular-expressions.info/lookaround.html

edited Oct 18, 2014 at 8:08

answered Oct 18, 2014 at 7:58

Mehdi Khademloo

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anubhava · Accepted Answer · 2014-10-18 08:15:30Z

1

Search for this regex:

([^a-zA-Z0-9])(?!^)\d+

Replace by:

$1

RegEx Demo

edited Oct 18, 2014 at 8:15

answered Oct 18, 2014 at 7:43

anubhava

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