# Python | Matching elements count

• Last Updated : 19 Feb, 2020

Sometimes, while working with lists we need to handle two lists and search for the matches, and return just the count of indices of the match. Querying whole list for the this process is not feasible when the size of master list is very large, hence having just the match indices helps in this cause. Let’s discuss certain ways in which this can be achieved.

Method #1 : Using list comprehension + `index() + len()`
This problem can potentially be solved using the index function of python to get the wanted indices and list comprehension can be used to extend this to the whole string. The len() is used to return total count of match.

 `# Python3 code to demonstrate``# Matching elements count``# using list comprehension and index() + len()`` ` `# initializing lists``test_list1 ``=` `[``5``, ``4``, ``1``, ``3``, ``2``]``test_list2 ``=` `[``1``, ``2``]`` ` `# printing original lists``print``(``"The original list 1 : "` `+` `str``(test_list1))``print``(``"The original list 2 : "` `+` `str``(test_list2))`` ` `# using list comprehension and index() + len()``# Matching elements count``res ``=` `len``([test_list1.index(i) ``for` `i ``in` `test_list2])`` ` `# print result``print``(``"The Match indices list count is : "` `+` `str``(res))`

Output :

```The original list 1 : [5, 4, 1, 3, 2]
The original list 2 : [1, 2]
The Match indices list count is : 2
```

Method #2 : Using `enumerate() + len()` + list comprehension
The enumerate function can be used to produce the key value pair for the list being it’s index and value and we can store them using list comprehension. The len() is used to return total count of match.

 `# Python3 code to demonstrate``# Matching elements count``# using list comprehension and enumerate() + len()`` ` `# initializing lists``test_list1 ``=` `[``5``, ``4``, ``1``, ``3``, ``2``]``test_list2 ``=` `[``1``, ``2``]`` ` `# printing original lists``print``(``"The original list 1 : "` `+` `str``(test_list1))``print``(``"The original list 2 : "` `+` `str``(test_list2))`` ` `# using list comprehension and enumerate() + len()``# Matching elements count``res ``=` `len``([key ``for` `key, val ``in` `enumerate``(test_list1) ``if` `val ``in` `set``(test_list2)])`` ` `# print result``print``(``"The Match indices list count is : "` `+` `str``(res))`

Output :

```The original list 1 : [5, 4, 1, 3, 2]
The original list 2 : [1, 2]
The Match indices list count is : 2
```

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