Python flavored regex

Don't expect all flavors of regular expressions to be the same. For example, one difference between Java and Python, Java allows "unions" of character class by nesting.

    [0-4[6-8]]

is the same as

    [0-46-8]

but Python's re module will only interpret the latter.

There is an alternative module on pypi called regex that may replace re, which handles nested sets.