String Matching with regular expressions

Question

I am trying to write a regular expression in Python which takes a string and checks if:

The last character is a vowel.
The last 2 characters are not the same.

This is what I came up with:

[aeiou]$

Can anybody help me with point number 2: last 2 characters are not the same. For example, expresso is valid and expressoo is not valid.

Huh? The first and last character of "expressoo" are not the same, so that should be valid. Did you mean "oxpresso"? — Karl Knechtel
– Karl Knechtel, Commented Dec 1, 2010 at 1:15

Angus · Accepted Answer · 2010-12-01 03:13:34Z

5

It might be easier to do this without a regular expression.

e.g if s[-2]!=s[-1] and s[-1] in 'aeiou'

edited Dec 1, 2010 at 3:13

answered Dec 1, 2010 at 1:18

Angus

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6 Comments

Steve Tjoa Over a year ago

The question changed. Nevertheless, +1.

K. Brafford Over a year ago

you would want to check for length first, in order to be complete, right? Something like: if len(s)>=2 and s[-1]!=s[-2] and s[-1] not in "AEIOUaeiou"

ricky2002 Over a year ago

I have to do it using regular expressions. I have done with that way already. Thank anyway...

mshsayem Over a year ago

Shouldn't it be s[-2] instead of s[0]?

Angus Over a year ago

The question changed after I answered it. Previously it was required that the first and last characters not be the same.

|

tchrist · Accepted Answer · 2010-12-01 01:53:28Z

2

(?i)([aeiouy])(?!\1)[aeiouy]$

EDIT:

This is also appealing for not having a repeat:

(?i)(?=[aeiouy]{2}$)(.)(?!\1).

edited Dec 1, 2010 at 1:53

answered Dec 1, 2010 at 1:23

tchrist

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5 Comments

I82Much Over a year ago

(note that you need to escape the backslash when you put it in your sourcecode).>>> re.match("(?i)([aeiouy])(?!\\1)[aeiouy]$", "ao") <_sre.SRE_Match object at 0x42eca0> >>> re.match("(?i)([aeiouy])(?!\\1)[aeiouy]$", "oo") >>>

tchrist Over a year ago

$ perl -le 'print for q(import re), q(print re.compile(r"(?i)([aeiouy])(?!\1)[aeiouy]$").search("paperboy").group(0))' | python

produces the string oy.

tchrist Over a year ago

@I82Much: You’re trying too hard. :)

tchrist Over a year ago

@Ricky2002: Don’t use web sites!!! Try it in your shell where you know WTH’s going on!

tchrist Over a year ago

The other solution reminds me of (?i)(?=.*a)(?=.*e)(?=.*i)(?=.*o)(?=.*u)(?=.*y).

Kabie · Accepted Answer · 2010-12-01 01:45:12Z

0

Best I can do:

r"\w*(?:[^a\W]a|[^e\W]e|[^i\W]i|[^u\W]u|[^o\W]o)\b"

answered Dec 1, 2010 at 1:45

Kabie

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