Pairing Heap implementation in Python

PairingHeap.py

##
## Pairing heap data structure
## More information on wiki:
## http://en.wikipedia.org/wiki/Pairing_heap
## 
## Data types
## Heap :: (Elem | None, Subs)
## Subs :: None | (Heap, Subs)
##

def heap(el=None):
    return (el, None)

def insert(h, el):
    return meld(h, heap(el))

def extract((_, subs)):
    return pairing(subs)

def min((el, subs)):
    return el

def meld((el1, subs1), (el2, subs2)):
    if el1 is None: return (el2, subs2)
    if el2 is None: return (el1, subs1)
    if el1 < el2:
        return (el1, ((el2, subs2), subs1))
    else:
        return (el2, ((el1, subs1), subs2))

def pairing(qs):
    if qs is None: return heap()
    (q1,tail) = qs
    if tail is None: return q1
    (q2, tail) = tail
    return pairing((meld(q1,q2), tail))


if __name__ == "__main__":
    print "=== Pairing heap ==="

    from random import randint

    ph = heap()
    for _ in xrange(20):
        ph = insert(ph, randint(1,20))

    # emulate heapsort
    while 1:
        if min(ph) is None: break
        print "->", min(ph)
        ph = extract(ph)

Nice clean version, but the last line of the pairing function is not quite right. It needs to be
return meld(meld(q1,q2), pairing(tail))
The current version has quadratic time complexity.
(See https://gist.github.com/alex1770/23292c136b1083c9adda06a8369bfb70 to see timings)