Python | Consecutive elements grouping in list

Last Updated : 09 Sep, 2019

Sometimes, while working with Python lists, we can have a problem in which we might need to group the list elements on basis of their respective consecutiveness. This kind of problem can occur while data handling. Let’s discuss certain way in which this task can be performed.

Method : Using enumerate() + groupby() + generator function + lambda
This task can be performed using the combination of above functions. In this, we create a generator function, in which we pass the list whose index-element are accessed using enumerate() and grouped by consecutive elements using groupby() and lambda. Works with Python2 only

# Python code to demonstrate working of
# Consecutive elements grouping list
# using enumerate() + groupby() + generator function + lambda
import itertools
  
# Utility Generator Function
def groupc(test_list):
    for x, y in itertools.groupby(enumerate(test_list), lambda (a, b): b - a):
        y = list(y)
        yield y[0][1], y[-1][1]
  
# initialize list
test_list = [1, 2, 3, 6, 7, 8, 11, 12, 13]
  
# printing original list
print("The original list is : " + str(test_list))
  
# Consecutive elements grouping list
# using enumerate() + groupby() + generator function + lambda
res = list(groupc(test_list))
  
# printing result
print("Grouped list is : " + str(res))

Output :

The original list is : [1, 2, 3, 6, 7, 8, 11, 12, 13]
Grouped list is : [(1, 3), (6, 8), (11, 13)]

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