String Matching with regular expressions

I am trying to write a regular expression in Python which takes a string and check开发者_如何学运维s if:

1. The last character is a vowel.
2. 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.

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

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

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

EDIT:

This is also appealing for not having a repeat:

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

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Best I can do:

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