Python | Segregating key’s value in list of dictionaries

While working with dictionaries, we may encounter with problem in which we need to segregate all the similar keys’ values together. This kind of problem can occur in web development domain while working with database. Let’s discuss certain ways in which this problem can be solved.

Method #1 : Using generator expression
A generator expression can be used to perform this particular task. In this we take one key at a time and check for the matching keys in all dictionaries. The drawback is that we need to know the key’s in advanced.

# Python3 code to demonstrate working of
# Segregating key's value in list of dictionaries
# Using generator expression

# Initialize list
test_list = [{'gfg' : 1, 'best' : 2}, {'gfg' : 4, 'best': 5}]

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

# Using generator expression
# Segregating key's value in list of dictionaries
res = [tuple(sub["gfg"] for sub in test_list),
      tuple(sub["best"] for sub in test_list)]

# printing result
print("Segregated values of keys are : " + str(res))

Output :

The original list : [{‘best’: 2, ‘gfg’: 1}, {‘best’: 5, ‘gfg’: 4}]
Segregated values of keys are : [(1, 4), (2, 5)]

Method #2 : Using zip() + map() + values()
The combination of above functions can also perform the similar task in one line. In this, values() is used to extract values, map() is used to link individual keys with one other and finally zip() joins the their corresponding values to single tuple.

# Python3 code to demonstrate working of
# Segregating key's value in list of dictionaries
# Using zip() + map() + values()

# Initialize list
test_list = [{'gfg' : 1, 'best' : 2}, {'gfg' : 4, 'best': 5}]

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

# Using zip() + map() + values()
# Segregating key's value in list of dictionaries
res = list(zip(*map(dict.values, test_list)))

# printing result
print("Segregated values of keys are : " + str(res))

Output :

The original list : [{‘best’: 2, ‘gfg’: 1}, {‘best’: 5, ‘gfg’: 4}]
Segregated values of keys are : [(1, 4), (2, 5)]