Python – Extract target key from other key values

Sometimes, while working with Python dictionaries, we can have a problem in which we need to extract particular key on basis of other matching record keys when there is exact match. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop + conditions
This is one of the ways in which this task can be performed. In this, we iterate for the dictionary keys and check for each keys for matching values.

# Python3 code to demonstrate working of
# Extract target key from other key values
# Using loop + condition

# initializing list
test_list = [{ 'name' : 'Manjeet', 'English' : 14, 'Maths' : 2},
             { 'name' : 'Akshat', 'English' : 7, 'Maths' : 13},
             { 'name' : 'Akash', 'English' : 1, 'Maths' : 17},
             { 'name' : 'Nikhil', 'English' : 10, 'Maths' : 18}]

# printing original list
print("The original list is : " + str(test_list))

# initializing filter items
filt_key = {'English' : 7, 'Maths' : 13}

# Extract target key from other key values
# Using loop + condition
res = []
for sub in test_list:
        if sub["English"] == filt_key["English"] and sub["Maths"] == filt_key["Maths"]:
            res.append(sub['name'])

# printing result
print("The filtered result : " + str(res))

Output :

The original list is : [{‘name’: ‘Manjeet’, ‘English’: 14, ‘Maths’: 2}, {‘name’: ‘Akshat’, ‘English’: 7, ‘Maths’: 13}, {‘name’: ‘Akash’, ‘English’: 1, ‘Maths’: 17}, {‘name’: ‘Nikhil’, ‘English’: 10, ‘Maths’: 18}]
The filtered result : [‘Akshat’]

Method #2 : Using loop + conditions ( for multiple/unknown keys )
This performs the task in similar way in which above method does. The advantage of using this method is that one doesn’t need to feed all keys manually in conditions.

# Python3 code to demonstrate working of
# Extract target key from other key values
# Using loop + conditions ( for multiple / unknown keys )

def hlper_func(test_keys, filt_key):
    for key in test_keys.keys():
        if key in filt_key:
            if test_keys[key] != int(filt_key[key]):
                return False
    return True

# initializing list
test_list = [{ 'name' : 'Manjeet', 'English' : 14, 'Maths' : 2},
             { 'name' : 'Akshat', 'English' : 7, 'Maths' : 13},
             { 'name' : 'Akash', 'English' : 1, 'Maths' : 17},
             { 'name' : 'Nikhil', 'English' : 10, 'Maths' : 18}]

# printing original list
print("The original list is : " + str(test_list))

# initializing filter items
filt_key = {'English' : 7, 'Maths' : 13}

# Extract target key from other key values
# Using loop + conditions ( for multiple / unknown keys )
res = []
for sub in test_list:
        if hlper_func(sub, filt_key):
            res.append(sub['name'])

# printing result
print("The filtered result : " + str(res))

Output :

The original list is : [{‘name’: ‘Manjeet’, ‘English’: 14, ‘Maths’: 2}, {‘name’: ‘Akshat’, ‘English’: 7, ‘Maths’: 13}, {‘name’: ‘Akash’, ‘English’: 1, ‘Maths’: 17}, {‘name’: ‘Nikhil’, ‘English’: 10, ‘Maths’: 18}]
The filtered result : [‘Akshat’]