在嵌套的Python字典中搜索键

Question

我有一些像这样的Python字典：

A = {id: {idnumber: condition},.... 

例如

A = {1: {11 : 567.54}, 2: {14 : 123.13}, .....

我需要搜索字典是否有任何idnumber == 11，并使用condition计算一些内容。但是如果在整个字典中没有任何idnumber == 11，我需要继续使用下一个字典。

这是我的尝试：

for id, idnumber in A.iteritems():
    if 11 in idnumber.keys(): 
       calculate = ......
    else:
       break

Answer 1

你很接近。

idnum = 11
# The loop and 'if' are good
# You just had the 'break' in the wrong place
for id, idnumber in A.iteritems():
    if idnum in idnumber.keys(): # you can skip '.keys()', it's the default
       calculate = some_function_of(idnumber[idnum])
       break # if we find it we're done looking - leave the loop
    # otherwise we continue to the next dictionary
else:
    # this is the for loop's 'else' clause
    # if we don't find it at all, we end up here
    # because we never broke out of the loop
    calculate = your_default_value
    # or whatever you want to do if you don't find it

如果需要知道内部有多少个11键，可以：

idnum = 11
print sum(idnum in idnumber for idnumber in A.itervalues())

这是因为密钥只能在每个dict中出现一次，所以您只需测试密钥是否存在。in返回True或False，等于1和0，因此sum是idnum的出现次数。

Answer 2

去救援

http://github.com/akesterson/dpath-python

dpath允许您通过globs进行搜索，这将得到您想要的内容。

$ easy_install dpath
>>> for (path, value) in dpath.util.search(MY_DICT, '*/11', yielded=True):
>>> ... # 'value' will contain your condition; now do something with it.

它将遍历字典中的所有条件，因此不需要特殊的循环构造。

另见

• how do i traverse nested dictionaries (python)?
• How to do this - python dictionary traverse and search
• Access nested dictionary items via a list of keys?
• Find all occurrences of a key in nested python dictionaries and lists
• Traverse a nested dictionary and get the path in Python?
• Find all the keys and keys of the keys in a nested dictionary
• Searching for keys in a nested dictionary
• Python: Updating a value in a deeply nested dictionary
• Is there a query language for JSON?
• Chained, nested dict() get calls in python