Question

Is there an equivalent of cons in Python? (any version above 2.5)

If so, is it built in? Or do I need easy_install do get a module?

Answer 1

In Python, it’s more typical to use the array-based list class than Lisp-style linked lists. But it’s not too hard to convert between them:

def cons(seq):
    result = None
    for item in reversed(seq):
        result = (item, result)
    return result

def iter_cons(seq):
    while seq is not None:
        car, cdr = seq
        yield car
        seq = cdr

>>> cons([1, 2, 3, 4, 5, 6])
(1, (2, (3, (4, (5, (6, None))))))
>>> iter_cons(_)
<generator object uncons at 0x00000000024D7090>
>>> list(_)
[1, 2, 3, 4, 5, 6]