Python - Print the common elements in all sublists

The Python language is primarily composed of different data structures and from it the list data structure is the most used one. The lists can hold elements of different data types and when they are assigned with some values they cannot be changed. The lists can even hold other lists within the square brackets “[]”. When two lists are defined to work on some platform, there may be some relations between them, and using this code the Python program makes it possible.

Printing common elements in the sublist

Let’s assume a list containing 10 elements and it can also be represented in the form of sublists like 3 elements in one sublist and the remaining seven elements in another sublist.

Syntax

list1 = [[1, 2, 3], [4, 5, 6, 7, 8, 9, 10]] 

The basic syntax contains the list data structure along with the sublists.

Approach

Approach 1 − Using the recursive function

Approach 2 − Using the reduce function

Approach 3 − Using the iteration method

Approach 1: Python Program to print common elements in all sublists using recursive function

The common elements from the sublists of the list are printed with the help of a recursive function, which the function calls itself recursively.

Algorithm

• Step 1 − Create the function common_elements().

• Step 2 − When the list’s length is equal to 1, it sets the list’s first element.

• Step 3 − Otherwise, it sets the intersection function to match the sublists for finding the common element using the slicing method.

• Step 3 − It returns the statement with common elements.

Example

#function is defined with a list argument
def common_elements(list1):
	if len(list1) == 1:
		return set(list1[0])
	else:
		return set(list1[0]).intersection(common_elements(list1[1:]))
#initializing the sublist inside the list data structure
list1 = [[2,3,4,5], [2,5], [2,10,5], [2,8,5,6], [2,10,9,5]]
common_elements = common_elements(list1)
#the length of the list should be greater than 0
if len(common_elements)>0:
	print("The common elements in the given sublists is:",common_elements)
else:
	print("The given list does not contain common elements! ")

Output

The common elements in the given sublist is: {2, 5}

Approach 2: Python Program to print common elements in all sublists using reduce function

In the method to print the common elements without any complex steps, the functools module is imported to use the reduce function.

Algorithm

• Step 1 − Import the required module.

• Step 2 − The list data structure is initialized with the sublists to find the common elements among them.

• Step 3 − The primary function behind this problem is achieved by the reduce and intersection functions.

• Step 4 − The map function simply maps the elements and converts each sublist into a set.

• Step 5 − Depending on the input defined, the print statement will return the common elements among the sublists.

Example

#importing the module
from functools import reduce
#initializing the sublist inside the list data structure
list1 = [[2,3,4,5], [2,5], [2,10,5], [2,8,5,6], [2,10,9,5]]
#with the help of the intersection function to match the elements among sublists
common_elements = reduce(set.intersection,map(set,list1))
#the length of the list should be greater than 0
if len(common_elements)>0:
	print("The common elements in the given sublists is:",common_elements)
else:
	print("The given list does not contain common elements! ")

Output

The common elements in the given sublist is: {2, 5}

Approach 3: Python Program to print common elements using for loop iteration method

The iteration through the lists makes the output print all possibilities of the common elements between the sublists.

Algorithm

• Step 1 − Creation of function with one list argument.

• Step 2 − Then create an empty set and take the first element of the array as list1[0].

• Step 3 − Use for loop for iteration.

• Step 4 − Verify the condition whether the length is greater than zero or not.

• Step 5 − Invoke the function common_element, and the output statement is printed.

Example

#defining the function with one list argument
def common_element(list1):
#creating an empty set and taking the first element of the array
	reference_set=set(list1[0])
#for is used to iterate through the given list
	for num in range(1,len(list1)):
#Adding the common element from the list to the created set
		fresh_set=set(tuple(list1[num]))
		reference_set&=fresh_set
#To check whether the length of the list greater than 0
	if len(reference_set) > 0:
		print("The common elements in the given sublists is:",reference_set)
	else:
		print("The given list does not contain common elements! ")
#initializing the list of sublists 
list1 = [[11,3,12,5], [12,11], [12,11,5], [12,11,5,6], [12,11,9,5]]
#calling the function to print the common elements
common_element(list1)

Output

The common elements in the given sublist is: {11, 12}

Conclusion

To find the common elements in a sublist, one should know how the sublist is assigned and its basic structure. The lists contain elements that are separated by common within the square brackets. The approaches are explained to print the common elements in the sublists of the list using the modules, recursive function, and the simple iteration method.