【发布时间】：2020-08-25 00:01:19
【问题描述】：
我正在研究一种使用各种霍夫曼编码的基因组压缩算法。我在 python2 中有以下代码：
def makeHuffTree(trees):
heapq.heapify(trees)
while len(trees) > 1:
childR, childL = heapq.heappop(trees), heapq.heappop(trees)
parent = (childL[0] + childR[0], childL, childR)
heapq.heappush(trees, parent)
return trees[0]
我正在尝试在 python3 中运行它。但是，我收到如下类型错误：
TypeError: '<' not supported between instances of 'tuple' and 'str'
进入函数的输入是一个元组列表。说，
[(1, '35'), (1, '38'), (1, '50'), (1, 'K'), (4, 'N')]
我很困惑，为什么它在 python 2 中工作但在 python3 中没有。 我尝试调试程序并将其缩小到出现错误的行。 模块heapq的功能如下：
def heappop(heap):
"""Pop the smallest item off the heap, maintaining the heap invariant."""
lastelt = heap.pop() # raises appropriate IndexError if heap is empty
if heap:
returnitem = heap[0]
heap[0] = lastelt
_siftup(heap, 0)
return returnitem
return lastelt
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)
def _siftdown(heap, startpos, pos):
newitem = heap[pos]
# Follow the path to the root, moving parents down until finding a place
# newitem fits.
while pos > startpos:
parentpos = (pos - 1) >> 1
parent = heap[parentpos]
if newitem < parent:
heap[pos] = parent
pos = parentpos
continue
break
heap[pos] = newitem
在线的siftup函数经过一些迭代后出现错误
if rightpos < endpos and not heap[childpos] < heap[rightpos]:
我尝试打印 rightpos 和 endpos 的类型，但我没有看到 str 的实例 - 每次它只是元组。
使用python2，函数执行成功，经过一些步骤后产生如下结果。
input (trees)= [(1, '35'), (1, '38'), (1, '50'), (1, 'K'), (4, 'N')]
[(1, '35'), (1, '38'), (1, '50'), (1, 'K'), (4, 'N')]
Step 1:
[(1, '50'), (1, 'K'), (4, 'N'), (2, (1, '38'), (1, '35'))]
Step 2:
[(2, (1, '38'), (1, '35')), (4, 'N'), (2, (1, 'K'), (1, '50'))]
Step 3:
[(4, 'N'), (4, (2, (1, 'K'), (1, '50')), (2, (1, '38'), (1, '35')))]
Step 4:
(8, (4, (2, (1, 'K'), (1, '50')), (2, (1, '38'), (1, '35'))), (4, 'N'))
Step 5:
但是 在 python 3 中，经过这么多步骤后出现错误。
input (trees)= [(1, '35'), (1, '38'), (1, '50'), (1, 'K'), (4, 'N')]
[(1, '35'), (1, '38'), (1, '50'), (1, 'K'), (4, 'N')]
Step 1:
[(1, '50'), (1, 'K'), (4, 'N'), (2, (1, '38'), (1, '35'))]
Step 2:
[(2, (1, '38'), (1, '35')), (4, 'N'), (2, (1, 'K'), (1, '50'))]
之后出现错误：“TypeError: 'tuple'和'str'的实例之间不支持'
我寻求帮助，让这段代码在 python3 中工作。
【问题讨论】：
-
令人惊讶的是，如果我更改输入元组，它也适用于 python3。假设我将最后一个元组从 (4,'N') 更改为 (1,'N')。它工作正常。现在，如果python本身的heapq模块出现错误，我会更加困惑。
-
问题是由于：python 2 允许在字符串和元组之间进行比较，但 python3 不允许比较。不过，正在寻找解决方法。
标签： python-3.x compression huffman-code genome heapq