给定一个简单的列表（parent，child），创建一个层次字典

Question

我有一个包含名称的元组列表。这些名称是父名称和子名称，我想用它们的名称创建一个层次字典树。 例如，我有以下列表：

[('john','marry'),('mike','john'),('mike','hellen'),('john','elisa')]

我想创造这个：

^{pr2}$

Answer 1

def get_children(parent, relations):
    children = (r[1] for r in relations if r[0] == parent)
    return {c: get_children(c, relations) for c in children}

the_list = [('john','marry'),('mike','john'),('mike','hellen'),('john','elisa')]

parents, children = map(set, zip(*the_list))
the_tree = {p: get_children(p, the_list) for p in (parents - children)}

print(the_tree)

Answer 2

假设它行为良好（没有循环、没有重复的名称或一个子对象有多个父对象），您可以简单地使用“有向图”并遍历它。为了找到根，我还使用了一个包含布尔值的字典，该布尔值表示该名称是否有父项：

lst = [('john','marry'), ('mike','john'), ('mike','hellen'), ('john','elisa')]

# Build a directed graph and a list of all names that have no parent
graph = {name: set() for tup in lst for name in tup}
has_parent = {name: False for tup in lst for name in tup}
for parent, child in lst:
    graph[parent].add(child)
    has_parent[child] = True

# All names that have absolutely no parent:
roots = [name for name, parents in has_parent.items() if not parents]

# traversal of the graph (doesn't care about duplicates and cycles)
def traverse(hierarchy, graph, names):
    for name in names:
        hierarchy[name] = traverse({}, graph, graph[name])
    return hierarchy

traverse({}, graph, roots)
# {'mike': {'hellen': {}, 'john': {'elisa': {}, 'marry': {}}}}

Answer 3

无论如何都可以选择：

data = [('john','marry'),('mike','john'),('mike','hellen'),('john','elisa')]

roots = set()
mapping = {}
for parent,child in data:
    childitem = mapping.get(child,None)
    if childitem is None:
        childitem =  {}
        mapping[child] = childitem
    else:
        roots.discard(child)
    parentitem = mapping.get(parent,None)
    if parentitem is None:
        mapping[parent] = {child:childitem}
        roots.add(parent)
    else:
        parentitem[child] = childitem

tree = {id : mapping[id] for id in roots}

print (tree)

结果：

^{pr2}$

记入@WillemVanOnsemRecursively creating a tree hierarchy without using class/object