General algorithm for allocation of series

Here is the generic algorithm of determining of the series from sequence by some feature SeriesFeature. Examples show usage of splitting series in camelCase strings (in the same case).

from abc import ABCMeta, abstractmethod
from itertools import groupby, imap

# a,b,c -> ((None, a), (a, b), (b, c)) (ie (prev, cur) pairs)
#preiter = lambda it: izip(chain([None], it), it)

class SeriesFeature(object):
    __metaclass__ = ABCMeta
    id = None # series id
    i = 0 # element index
    def __init__(self, serid):
        self.i = -1
        self.id = serid
    @abstractmethod
    def __series__(self, el, serid):
        """Check element `el` and return new/old series id. `serid`
        is current series id`
        """
    def __call__(self, el):
        self.i += 1
        self.id = self.__series__(el, self.id)
        return self.id

class CapitalizedSeries(SeriesFeature):
    def __init__(self):
        super(CapitalizedSeries, self).__init__(0)
    def __series__(self, el, serid):
        if self.i == 0 and el.isupper():
            return serid
        elif el.islower():
            return serid
        else:
            return (serid + 1)%2

CamelCaseSeries = CapitalizedSeries

def iseries(flt, it):
    series = (el[1] for el in groupby(it, flt()))
    if isinstance(it, str):
        return imap(''.join, series)
    else:
        return series

def camelcaseto(s, func):
    """Transform each CamelCase-string part with `func(ser)`"""
    return imap(func, iseries(CamelCaseSeries, s))

########################## test ##############################################
print list(iseries(CapitalizedSeries, 'AaaaBbbCcAaa'))
print list(iseries(CapitalizedSeries, 'abcDefGhi'))

print ' '.join(camelcaseto("noSuchUserError", str.lower)).capitalize()