# Python | Count of common elements in the lists

• Last Updated : 24 Sep, 2022

Sometimes, while working with Python list we can have a problem in which we have to compare two lists for index similarity and hence can have a task of counting equal index pairs. Let’s discuss certain ways in which this task can be performed.

Method #1 : Using sum() + zip() This task can be performed by passing the zip(), which performs task of mapping both list with each other, to the sum() which computes the sum according to equal indices.

## Python3

 `# Python3 code to demonstrate working of``# Identical element summation in lists``# using sum() + zip()` `# initialize lists``test_list1 ``=` `[``5``, ``6``, ``10``, ``4``, ``7``, ``1``, ``19``]``test_list2 ``=` `[``6``, ``6``, ``10``, ``3``, ``7``, ``10``, ``19``]` `# printing original lists``print``(``"The original list 1 is : "` `+` `str``(test_list1))``print``(``"The original list 2 is : "` `+` `str``(test_list2))` `# Identical element summation in lists``# using sum() + zip()``res ``=` `sum``(x ``=``=` `y ``for` `x, y ``in` `zip``(test_list1, test_list2))` `# printing result``print``(``"Summation of Identical elements : "` `+` `str``(res))`

Output :

```The original list 1 is : [5, 6, 10, 4, 7, 1, 19]
The original list 2 is : [6, 6, 10, 3, 7, 10, 19]
Summation of Identical elements : 4```

Method #2 : Using sum() + map() + eq The task performed in above method using zip() can be executed here using the map function which performs similar task. The equality check can be performed by inbuilt eq operator.

## Python3

 `# Python3 code to demonstrate working of``# Identical element summation in lists``# using sum() + map() + eq``from` `operator ``import` `eq` `# initialize lists``test_list1 ``=` `[``5``, ``6``, ``10``, ``4``, ``7``, ``1``, ``19``]``test_list2 ``=` `[``6``, ``6``, ``10``, ``3``, ``7``, ``10``, ``19``]` `# printing original lists``print``(``"The original list 1 is : "` `+` `str``(test_list1))``print``(``"The original list 2 is : "` `+` `str``(test_list2))` `# Identical element summation in lists``# using sum() + map() + eq``res ``=` `sum``(``map``(eq, test_list1, test_list2))` `# printing result``print``(``"Summation of Identical elements : "` `+` `str``(res))`

Output :

```The original list 1 is : [5, 6, 10, 4, 7, 1, 19]
The original list 2 is : [6, 6, 10, 3, 7, 10, 19]
Summation of Identical elements : 4```

Method #3: Using set() + len() The task performed can also be perform using the set and len function. We can get a common element using set intersection and count the total common element using len function.

## Python3

 `# Python3 code to demonstrate working of``# Identical element summation in lists``# using set() + let()` `# initialize lists``test_list1 ``=` `[``5``, ``6``, ``10``, ``4``, ``7``, ``1``, ``19``]``test_list2 ``=` `[``6``, ``6``, ``10``, ``3``, ``7``, ``10``, ``19``]` `# printing original lists``print``(``"The original list 1 is : "` `+` `str``(test_list1))``print``(``"The original list 2 is : "` `+` `str``(test_list2))` `# Identical element summation in lists``# using set() + len()``res ``=` `len``(``set``(test_list1) & ``set``(test_list2));` `# printing result``print``(``"Summation of Identical elements : "` `+` `str``(res))`

Output

```The original list 1 is : [5, 6, 10, 4, 7, 1, 19]
The original list 2 is : [6, 6, 10, 3, 7, 10, 19]
Summation of Identical elements : 4
```

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