Python get key of a value inside a nested dictionary-CodePudding

Let's say I have a dictionary called my_dic:

my_dict = {'a': {'spam': {'foo': None, 'bar': None, 'baz': None},'eggs': None}, 'b': {'ham': None}}

Then if I input spam, it should return a, and if I input bar it should return spam. If I input b, it should return None. Basically getting the parent of the dictionary.

How would I go about doing this?

CodePudding user response：

A simple recursive function, which returns the current key if needle in v is true; needle in v simply testing if the key exists in the associated value:

my_dict = {'a': {'spam': {'foo': None, 'bar': None, 'baz': None},'eggs': None}, 'b': {'ham': None}}

def get_parent_key(d: dict, needle: str):
    for k, v in d.items():
        if isinstance(v, dict):
            if needle in v:
                return k
            
            if found := get_parent_key(v, needle):
                return found
                
print(get_parent_key(my_dict, 'bar'))

CodePudding user response：

To check if a key exists in a dictionary and get its corresponding value, you can use the in keyword and the .get() method.

Here's an example:

my_dict = {'a': {'spam': {'foo': None, 'bar': None, 'baz': None},'eggs'}, 'b': {'ham'}}

# Check if 'spam' is a key in my_dict and get its value
if 'spam' in my_dict:
  print(my_dict['spam']) # Output: {'foo': None, 'bar': None, 'baz': None}
else:
  print('Key not found')

# Check if 'bar' is a key in my_dict and get its value
if 'bar' in my_dict:
  print(my_dict['bar']) # Output: Key not found
else:
  print('Key not found')

# Use .get() to check if 'b' is a key in my_dict and get its value
value = my_dict.get('b')
if value is not None:
  print(value) # Output: {'ham'}
else:
  print('Key not found')