Part of as string from a string using regular expressions

Question

I have a string of 5 characters out of which the first two characters should be in some list and next three should be in some other list.

How could i validate them with regular expressions?

Example:

List for First two characters {VBNET, CSNET, HTML)}
List for next three characters {BEGINNER, EXPERT, MEDIUM}

My Strings are going to be: VBBEG, CSBEG, etc.

My regular expression should find that the input string first two characters could be either VB, CS, HT and the rest should also be like that.

Miika L. · Accepted Answer · 2012-04-17 07:00:44Z

1

Would the following expression work for you in a more general case (so that you don't have hardcoded values): (^..)(.*$) - returns the first two letters in the first group, and the remaining letters in the second group.

edited Apr 17, 2012 at 7:00

answered Apr 17, 2012 at 6:47

Miika L.

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2 Comments

Rupesh Over a year ago

Thanks for that. My First two characters extracted should match the first two characters of the word in the list specified. Any threads on this? Thanks in advance...

Miika L. Over a year ago

@Rupesh The list matching would depend on what programming language you are using.

fardjad · Accepted Answer · 2012-04-17 06:35:06Z

1

something like this:

^(VB|CS|HT)(BEG|EXP|MED)$

answered Apr 17, 2012 at 6:35

fardjad

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Comments

mjbnz · Accepted Answer · 2012-04-17 06:35:25Z

1

This recipe works for me:

^(VB|CS|HT)(BEG|EXP|MED)$

answered Apr 17, 2012 at 6:35

mjbnz

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Matthias · Accepted Answer · 2012-04-17 06:35:07Z

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I guess (VB|CS|HT)(BEG|EXP|MED) should do it.

answered Apr 17, 2012 at 6:35

Matthias

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Comments

Li-aung Yip · Accepted Answer · 2012-04-17 07:07:08Z

0

If your strings are as well-defined as this, you don't even need regex - simple string slicing would work.

For example, in Python we might say:

mystring = "HTEXP"

prefix = mystring[0:2]
suffix = mystring[2:5]

if (prefix in ['HT','CS','VB']) AND (suffix in ['BEG','MED','EXP']):
    pass # valid!
else:
    pass # not valid. :(

Don't use regex where elementary string operations will do.

answered Apr 17, 2012 at 7:07

Li-aung Yip

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1 Comment

Li-aung Yip Over a year ago

@Rupesh: A regexp can certainly be used to solve this problem - in this case the complexity of the code is about the same. My general advice, however, is to think carefully before using regular expressions for everything. Often "plain" string methods will do just fine.

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