I also think the naming is really bad and can be improved. The central problem is that you're using action words for a descriptive API. You should use something

I also think the naming is really bad and can be improved. The central problem is that you're using action words for a descriptive API. You should use something like "Repeating" instead of "Times". Also, the parameters to Times are distinctly un-pythonic. I would probably make it provide this API: def Repeating(pattern, *args, min=None, max=None, exact=None):... Repeating(P) => P* Repeating(P, a, b) and Repeating(P, min=a, max=b) => P{a, b} Repeating(P, n) and Repeating(P, exact=n) => P{n, n} Repeating(P, min=n) => P{n,} Repeating(P, max=n) => P{0, n} "Exclude" and "Include" suffer from the aforementioned problem of being procedural words for a declarative syntax. And they're easy to confuse with one another, having only two differing letters. And they don't make it clear that they match exactly one character. I would use "AnyBut" and "OneOf". Why the split between Group and NamedGroup? Just add a name parameter to Group! Seq as mentioned by parent is also problematic. Use Range or maybe Between or FromTo. To me FromTo flows the best, but Range is also ok. I'm tempted to advocate adding operator overloading, so | would make a pattern that matches any one of two alternatives, * would be used for specifying repeats, etc. So you could write Digit = FromTo('0', '9') CapitalLetter = FromTo('A', 'Z') POCode = CapitalLetter * 2 + Digit * 3 SmallLetter = FromTo('a', 'z') Letter = CapitalLetter or SmallLetter Name = CapitalLetter + Letter * (0, Inf) FirstName = Group(name='first', Name) LastName = Group(name='last', Name) FullName = FirstName + ' ' + LastName However, implemented badly that can hurt readability much more than having to write functions everywhere.