sort(),但是这很尴尬,最好直接在python中实现拓扑排序。
为什么会很尴尬?如果您在Wiki页面上研究这两种算法,它们都依赖于运行中的一组“标记节点”,很难
sort()使用这种概念来扭曲形式,因为
key=xxx(甚至
cmp=xxx)最适合与无状态比较函数一起使用,尤其是因为timsort不保证该元素将被检查的顺序。我(美丽的)肯定,任何解决方案
确实 使用
sort()将要结束了冗余计算每个呼叫键/ CMP功能的一些信息,以避开无国籍问题。
以下是我一直在使用的算法(对一些Javascript库依赖关系进行排序):
编辑:基于Winston Ewert的解决方案对此做了很大的修改
def topological_sort(source): """perform topo sort on elements. :arg source: list of ``(name, [list of dependancies])`` pairs :returns: list of names, with dependancies listed first """ pending = [(name, set(deps)) for name, deps in source] # copy deps so we can modify set in-placeemitted = [] while pending: next_pending = [] next_emitted = [] for entry in pending: name, deps = entry deps.difference_update(emitted) # remove deps we emitted last pass if deps: # still has deps? recheck during next pass next_pending.append(entry) else: # no more deps? time to emit yield name emitted.append(name) # <-- not required, but helps preserve original ordering next_emitted.append(name) # remember what we emitted for difference_update() in next pass if not next_emitted: # all entries have unmet deps, one of two things is wrong... raise ValueError("cyclic or missing dependancy detected: %r" % (next_pending,)) pending = next_pending emitted = next_emitted
旁注:它 是
可能的鞋拔一个
cmp()函数成
key=xxx,如在本蟒错误跟踪概述消息。
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