# Python – Filter key’s value from other key

• Last Updated : 02 Jun, 2020

Sometimes, while working with Python dictionary, we can have a problem in which we need to extract a value from dictionary list of the key on basis of some other key equality. This kind of problem is common in domains that include data, for e.g web development. Let’s discuss certain ways in which this task can be performed.

Input :
test_list = [{‘gfg’ : 5, ‘is’ : 8, ‘best’ : 24}, {‘gfg’ : 7, ‘is’ : 12, ‘best’ : 24}]
req_key = ‘gfg’ [ Requested Key ]
fil_key = ‘best’ [ Filtering Key ]
fil_val = 24 [ Filtering value to be checked ]
Output : [5, 7]

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Input :
test_list = [{‘gfg’ : 5, ‘is’ : 8, ‘best’ : 24}]
req_key = ‘gfg’ [ Requested Key ]
fil_key = ‘best’ [ Filtering Key ]
fil_val = 24 [ Filtering value to be checked ]
Output : 

Method #1 : Using loop
This is brute force way to solve this problem. In this, we manually iterate the entire list and check for filter key’s value, on equality we extract the required key’s value.

 `# Python3 code to demonstrate working of ``# Filter key's value from other key``# Using loop`` ` `# initializing list``test_list ``=` `[{``'gfg'` `: ``5``, ``'is'` `: ``8``, ``'best'` `: ``12``}, ``             ``{``'gfg'` `: ``7``, ``'is'` `: ``12``, ``'best'` `: ``24``},``             ``{``'gfg'` `: ``20``, ``'is'` `: ``17``, ``'best'` `: ``18``}]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing required key``req_key ``=` `'gfg'`` ` `# initializing filter key``fil_key ``=` `'best'`` ` `# initializing filter val ``fil_val ``=` `24`` ` `# Filter key's value from other key``# Using loop``res ``=` `[]``for` `sub ``in` `test_list:``  ``if` `sub[fil_key] ``=``=` `fil_val:``    ``res.append(sub[req_key])`` ` `# printing result ``print``(``"The required value : "` `+` `str``(res)) `
Output :

The original list is : [{‘gfg’: 5, ‘is’: 8, ‘best’: 12}, {‘gfg’: 7, ‘is’: 12, ‘best’: 24}, {‘gfg’: 20, ‘is’: 17, ‘best’: 18}]
The required value : 

Method #2 : Using list comprehension
This is yet another way to solve this problem. In this, we perform the task similar in above method, in a shorthand way using list comprehension construct.

 `# Python3 code to demonstrate working of ``# Filter key's value from other key``# Using list comprehension`` ` `# initializing list``test_list ``=` `[{``'gfg'` `: ``5``, ``'is'` `: ``8``, ``'best'` `: ``12``}, ``             ``{``'gfg'` `: ``7``, ``'is'` `: ``12``, ``'best'` `: ``24``},``             ``{``'gfg'` `: ``20``, ``'is'` `: ``17``, ``'best'` `: ``18``}]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing required key``req_key ``=` `'gfg'`` ` `# initializing filter key``fil_key ``=` `'best'`` ` `# initializing filter val ``fil_val ``=` `24`` ` `# Filter key's value from other key``# Using list comprehension``res ``=` `[sub[req_key] ``for` `sub ``in` `test_list ``if` `sub[fil_key] ``=``=` `fil_val]`` ` `# printing result ``print``(``"The required value : "` `+` `str``(res)) `
Output :

The original list is : [{‘gfg’: 5, ‘is’: 8, ‘best’: 12}, {‘gfg’: 7, ‘is’: 12, ‘best’: 24}, {‘gfg’: 20, ‘is’: 17, ‘best’: 18}]
The required value : 

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