Bug in Python?
ian.g.kelly at gmail.com
Fri Feb 26 17:37:15 EST 2016
On Fri, Feb 26, 2016 at 3:08 PM, Sven R. Kunze <srkunze at mail.de> wrote:
> Python sometimes seems not to hop back and forth between C and Python code.
C code as a rule tends to ignore dunder methods. Those are used to
implement Python operations, not C operations.
> _siftup(heap, 0) # that's C
Your comment here appears to be incorrect.
>>> from heapq import _siftup
>>> import inspect
def _siftup(heap, pos):
endpos = len(heap)
startpos = pos
newitem = heap[pos]
# Bubble up the smaller child until hitting a leaf.
childpos = 2*pos + 1 # leftmost child position
while childpos < endpos:
# Set childpos to index of smaller child.
rightpos = childpos + 1
if rightpos < endpos and not heap[childpos] < heap[rightpos]:
childpos = rightpos
# Move the smaller child up.
heap[pos] = heap[childpos]
pos = childpos
childpos = 2*pos + 1
# The leaf at pos is empty now. Put newitem there, and bubble it up
# to its final resting place (by sifting its parents down).
heap[pos] = newitem
_siftdown(heap, startpos, pos)
So I would guess that the difference here is because one
implementation is entirely C, and the other implementation is entirely
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