Python | Group and count similar records

Sometimes, while working with records, we can have a problem in which we need to collect and maintain the counter value inside records. This kind of application is important in web development domain. Let’s discuss certain ways in which this task can be performed. 

Method #1 : Using loop + Counter() + set() The combination of above functionalities can be employed to achieve this task. In this, we run a loop to capture each tuple and add to set and check if it’s already existing, then increase and add a counter value to it. The cumulative count is achieved by using Counter(). 

Python3

# Python3 code to demonstrate working of
# Group and count similar records
# using Counter() + loop + set()
from collections import Counter

# initialize list
test_list = [('gfg', ), ('is', ), ('best', ), ('gfg', ),
             ('is', ), ('for', ), ('geeks', )]

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

# Group and count similar records
# using Counter() + loop + set()
res = []
temp = set()
counter = Counter(test_list)
for sub in test_list:
    if sub not in temp:
        res.append((counter[sub], ) + sub)
        temp.add(sub)

# printing result
print("Grouped and counted list is : " + str(res))

Output

The original list : [('gfg',), ('is',), ('best',), ('gfg',), ('is',), ('for',), ('geeks',)]
Grouped and counted list is : [(2, 'gfg'), (2, 'is'), (1, 'best'), (1, 'for'), (1, 'geeks')]

Method #2 : Using Counter() + list comprehension + items() This is one liner approach and recommended to use for programming. The task of loops is handled by list comprehension and items() is used to access all the elements of Counter converted dictionary to allow computations. 

Python3

# Python3 code to demonstrate working of
# Group and count similar records
# using Counter() + list comprehension + items()
from collections import Counter

# initialize list
test_list = [('gfg', ), ('is', ), ('best', ), ('gfg', ),
             ('is', ), ('for', ), ('geeks', )]

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

# Group and count similar records
# using Counter() + list comprehension + items()
res = [(counter, ) + ele for ele, counter in Counter(test_list).items()]

# printing result
print("Grouped and counted list is : " + str(res))

Output

The original list : [('gfg',), ('is',), ('best',), ('gfg',), ('is',), ('for',), ('geeks',)]
Grouped and counted list is : [(2, 'gfg'), (2, 'is'), (1, 'best'), (1, 'for'), (1, 'geeks')]

Method #3 : Using count(),join(),list() and set() methods

Python3

# Python3 code to demonstrate working of
# Group and count similar records

# initialize list
test_list = [('gfg', ), ('is', ), ('best', ), ('gfg', ),
             ('is', ), ('for', ), ('geeks', )]

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

# Group and count similar records
res = []
x = list(set(test_list))
for i in x:
    a = test_list.count(i)
    b = "".join(i)
    res.append((a, b))
# printing result
print("Grouped and counted list is : " + str(res))

Output

The original list : [('gfg',), ('is',), ('best',), ('gfg',), ('is',), ('for',), ('geeks',)]
Grouped and counted list is : [(2, 'gfg'), (1, 'best'), (1, 'geeks'), (1, 'for'), (2, 'is')]

Method 4:  using operator.countOf() method

Python3

# Python3 code to demonstrate working of
# Group and count similar records
import operator as op
# initialize list
test_list = [('gfg', ), ('is', ), ('best', ), ('gfg', ),
             ('is', ), ('for', ), ('geeks', )]

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

# Group and count similar records
res = []
x = list(set(test_list))
for i in x:
    a = op.countOf(test_list, i)
    b = "".join(i)
    res.append((a, b))
# printing result
print("Grouped and counted list is : " + str(res))

Output

The original list : [('gfg',), ('is',), ('best',), ('gfg',), ('is',), ('for',), ('geeks',)]
Grouped and counted list is : [(2, 'gfg'), (1, 'best'), (1, 'for'), (1, 'geeks'), (2, 'is')]

Time Complexity: O(N)
Auxiliary Space : O(N)