问python ete2二叉树得到后代值的和。

EN

from ete2 import Tree
t = Tree("(((b,c), a), (d,e));")

print "Method 1: caching node content"
internal_node_content = t.get_cached_content(store_attr="name")
for node, content in internal_node_content.iteritems():
    if not node.is_leaf():
        print node, "\nConcat:", ''.join(content)


print "Method 2: post order iteration"
node2concat = {}
for node in t.traverse("postorder"):
    if not node.is_leaf():
        concat = ''.join([node2concat[ch] for ch in node.children])
        node2concat[node] = concat
        print node, "\nConcat:", concat
    else:
        node2concat[node] = node.name


#Method 1: caching node content
# 
#         /-b
#      /-|
#   /-|   \-c
#  |  |
#--|   \-a
#  |
#  |   /-d
#   \-|
#      \-e 
#Concat: acbed
# 
#   /-b
#--|
#   \-c 
#Concat: cb
# 
#      /-b
#   /-|
#--|   \-c
#  |
#   \-a 
#Concat: acb
# 
#   /-d
#--|
#   \-e 
#Concat: ed
#Method 2: post order iteration
# 
#   /-b
#--|
#   \-c 
#Concat: bc
# 
#      /-b
#   /-|
#--|   \-c
#  |
#   \-a 
#Concat: bca
# 
#   /-d
#--|
#   \-e 
#Concat: de
# 
#         /-b
#      /-|
#   /-|   \-c
#  |  |
#--|   \-a
#  |
#  |   /-d
#   \-|
#      \-e 
#Concat: bcade