How can I find the value of the key in a recursive dictionary?
I wrote a recursive function to find a value with data dict
and key
. But I think there should be a more readable version. Here's a block of code.
def findvalue(_dict, target):
for key, values in _dict.items():
if 'dict' in str(type(values)):
return findvalue(values, target)
elif key == target:
return values
else:
print("no such key")
Is there any one version of this or using yield (not sure about this)?
Edit : Based on recursive functions and add / extension lists and ideas from comments. I modified the function to find all matched values using a given key
def find_all_value(_dict, target, values=None):
for key, values in _dict.items():
#case 1: it is a dictionary but not match the key
if isinstance(values, dict) and key!=target:
return find_all_value(values, target)
#case 2: it is a dictionary but match the key -> put it in result
elif isinstance(values, dict) and key==target:
return [values] + find_all_value(values, target)
#case 3: it is not dictionary and match the key -> put it in result
elif key==target:
return [values]
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Edit:
Recursively searching for (nested) dict (s) through list comprehension:
def findvalue(d, key):
l = [e for e in [findvalue(e, key) for e in [d[k] for k in d.keys() if type(d[k])==dict]] if e]
l.append(d[key]) if key in d else l
return l
^ Returns (nested) lists of values for each matching (nested) dict key.
A simplified version that prints, rather than returns, each match:
def findvalue(d, key):
[findvalue(e, key) for e in [d[k] for k in d.keys() if type(d[k])==dict]]
if key in d: print(d[key])
^ Just displays the values for each matching key as they occur.
Test using
d = {1:2, 3:4, 5:{6:7,8:9, 99:{100:101}}, 10:11}
<Hitp> def findvalue (dict, key, target): if dict [key] == target: return True return False
Check it:
dict = {1:2,3:4} findvalue(dict,3,4)
Strike>
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To find the value of the first key (found in Breadth First Search) of a python recursive dictionary.
You can do:
def find_value(_dict, key):
stack = [(None, _dict)]
while len(stack) != 0:
_key, val = stack.pop(0)
if val is not _dict and _key == key:
return val
if isinstance(val, dict):
for k, v in val.items():
stack.append((k, v))
Example:
d = {'c': {'d': 3, 'e': 4}, None: 0, 'b': 2, 'a': 1}
print('None:', find_value(d, None))
print('c:', find_value(d, 'c'))
print('e:', find_value(d, 'e'))
print('a:', find_value(d, 'a'))
Output:
None: 0
c: {'e': 4, 'd': 3}
e: 4
a: 1
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