我是Python的新手，并且知道有一种更好的方法来构造递归查询。希望有更多高级的人来看看如何最好地简化以下代码。
我在StackOverflow上倾倒了类似的示例，但是没有一个我想要遍历的数据结构。
样本数据：
[
{'categoryId': 100, 'parentId': 0, 'catName': 'Animals & Pet Supplies'},
{'categoryId': 103, 'parentId': 100, 'catName': 'Pet Supplies'},
{'categoryId': 106, 'parentId': 103, 'catName': 'Bird Supplies'},
{'categoryId': 500, 'parentId': 0, 'catName': 'Apparel & Accessories'},
{'categoryId': 533, 'parentId': 500, 'catName': 'Clothing'},
{'categoryId': 535, 'parentId': 533, 'catName': 'Activewear'}
]
Python代码：
def returnChildren(categoryId):
cats = dict()
results = categories.find( { "parentId" : categoryId } )
for x in results:
cats[x['categoryId']] = x['catName']
return cats
children = returnChildren(cat_id)
#build list of children for this node
for x in children:
print (x, "-", children[x])
results = returnChildren(x)
if (len(results) > 0):
for y in sorted(results.keys()):
print(y, "--", results[y])
sub_results = returnChildren(y)
if (len(sub_results) > 0):
for z in sorted(sub_results.keys()):
print(z, "----", sub_results[z])
sub_sub_results = returnChildren(z)
if (len(sub_sub_results) > 0):
for a in sorted(sub_sub_results.keys()):
print(a, "------", sub_sub_results[a])
此代码将生成类似于以下内容的树：
100 Animals & Pet Supplies
103 - Pet Supplies
106 -- Bird Supplies
500 Apparel & Accessories
533 - Clothing
535 -- Activewear
您可以使用递归函数遍历树。
另外，可能有必要预先计算出亲本树（它对于其他目的也可能有用）。
我在这里将内容包装到一个类中–遵循起来应该很简单。
（编辑：代替早期版本中的回调函数，我已将其改为使用生成器，从而更加Pythonic。）
from collections import defaultdict
class NodeTree:
def __init__(self, nodes):
self.nodes = nodes
self.nodes_by_parent = defaultdict(list)
for node in self.nodes:
self.nodes_by_parent[node["parentId"]].append(node)
def visit_node(self, node, level=0, parent=None):
yield (level, node, parent)
for child in self.nodes_by_parent.get(node["categoryId"], ()):
yield from self.visit_node(child, level=level + 1, parent=node)
def walk_tree(self):
"""
Walk the tree starting from the root, returning 3-tuples (level, node, parent).
"""
for node in self.root_nodes:
yield from self.visit_node(node)
@property
def root_nodes(self):
return self.nodes_by_parent.get(0, ())
nodes = [
{"categoryId": 100, "parentId": 0, "catName": "Animals & Pet Supplies"},
{"categoryId": 103, "parentId": 100, "catName": "Pet Supplies"},
{"categoryId": 106, "parentId": 103, "catName": "Bird Supplies"},
{"categoryId": 500, "parentId": 0, "catName": "Apparel & Accessories"},
{"categoryId": 533, "parentId": 500, "catName": "Clothing"},
{"categoryId": 535, "parentId": 533, "catName": "Activewear"},
]
tree = NodeTree(nodes)
for level, node, parent in tree.walk_tree():
print(node["categoryId"], "-" * level, node["catName"])
此代码几乎像您的原始版一样打印，
100 Animals & Pet Supplies
103 - Pet Supplies
106 -- Bird Supplies
500 Apparel & Accessories
533 - Clothing
535 -- Activewear
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