[英]Python ordered list based on property
我有以下要根據依賴關系排序的對象的列表。 首先,將沒有依賴關系的對象首先添加到列表中,然后對添加的第一個批次具有依賴關系的批次,依此類推,直到從列表中刪除所有項目為止。
pp = [
{"name": 'pipeline13', "deps": 'pipeline11' },
{"name": 'pipeline1', "deps": 'pipeline4' },
{"name": 'pipeline4'},
{"name": 'pipeline2', "deps": 'pipeline4'},
{"name": 'pipeline3'},
{"name": 'pipeline5'},
{"name": 'pipeline6', "deps": 'pipeline2'},
{"name": 'pipeline7'},
{"name": 'pipeline8', "deps": 'pipeline2'},
{"name": 'pipeline9', "deps": 'pipeline3'},
{"name": 'pipeline10', "deps": 'pipeline1' },
{"name": 'pipeline11', "deps": 'pipeline10' }
]
目前,我有下面的代碼可以工作,但它不是可擴展的,也不是非常Pythonic。
output = []
output_stage_1 = []
output_stage_2 = []
output_stage_3 = []
output_stage_4 = []
output_stage_5 = []
while pp:
for p in pp:
if not p.get('deps'):
output.append(p)
pp.remove(p)
if p.get('deps') in [i.get('name') for i in output]:
output_stage_1.append(p)
pp.remove(p)
if p.get('deps') in [i.get('name') for i in output_stage_1]:
output_stage_2.append(p)
pp.remove(p)
if p.get('deps') in [i.get('name') for i in output_stage_2]:
output_stage_3.append(p)
pp.remove(p)
if p.get('deps') in [i.get('name') for i in output_stage_3]:
output_stage_4.append(p)
pp.remove(p)
if p.get('deps') in [i.get('name') for i in output_stage_4]:
output_stage_5.append(p)
pp.remove(p)
print(output + output_stage_1 + output_stage_2 + output_stage_3 + output_stage_4 + output_stage_5)
您可以這樣做:
ordered = [ item["name"] for item in pp if "deps" not in item ]
while len(ordered) < len(pp):
for item in pp:
if "deps" not in item : continue
if item["name"] not in ordered and item["deps"] in ordered:
ordered.append(item["name"])
請注意,我沒有對其進行優化,因此在大型數據集上可能會有點慢。
[編輯]這是一個優化的版本:
ordered = [ item for item in pp if "deps" not in item ]
dependents = [ (item["name"],item["deps"],item) for item in pp if "deps" in item]
included = set([item["name"] for item in ordered])
remaining = len(dependents)
while remaining > 0:
nextGroup = []
circularCount = remaining
for name,deps,item in dependents:
if deps in included:
ordered.append(item)
included.add(name)
remaining -= 1
else:
nextGroup.append((name,deps,item))
dependents = nextGroup
if remaining == circularCount : break
if remaining > 0 :
# There was a circular dependency error
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