A Python 3.4 conj function for mutable and immutable sequences and strings.

conj.py

from functools import singledispatch
from collections import Sequence, MutableSequence

@singledispatch
def conj(sequence, item):
    raise TypeError("conj() not supported for type '{}'".format(type(sequence)))
    
@conj.register(MutableSequence)
def _(sequence, item):
    sequence.append(item)
    return sequence
    
@conj.register(Sequence)
def _(sequence, item):
    return sequence + type(sequence)((item,))
    
@conj.register(str)
@conj.register(bytes)
def _(sequence, item):
    return sequence + item