# Python | Count of elements matching particular condition

Checking a number/element by a condition is a common problem one faces and is done in almost every program. Sometimes we also require to get the totals that match the particular condition to have a distinguish which to not match for further utilization. Lets discuss certain ways in which this task can be achieved.

Method #1 : Using `sum()` + generator expression
This method uses the trick of adding 1 to the sum whenever the generator expression returns true. By the time list gets exhausted, summation of count of numbers matching a condition is returned.

 `# Python 3 code to demonstrate  ` `# to get count of elements matching condition  ` `# using sum() + generator expression ` ` `  `# initializing list ` `test_list ``=` `[``3``, ``5``, ``1``, ``6``, ``7``, ``9``] ` ` `  `# printing original list ` `print` `(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# using sum() + generator expression ` `# to get count of elements matching condition  ` `# checks for odd ` `res ``=` `sum``(``1` `for` `i ``in` `test_list ``if` `i ``%` `2` `!``=` `0``) ` ` `  `# printing result ` `print` `(``"The number of odd elements: "` `+` `str``(res)) `

Output :

```The original list is : [3, 5, 1, 6, 7, 9]
The number of odd elements: 5
```

Method #2 : Using `sum()` + `map()```` map()``` does the task almost similar to the generator expression, difference is just the internal data structure employed by it is different hence more efficient.

 `# Python 3 code to demonstrate  ` `# to get count of elements matching condition  ` `# using sum()+ map() ` ` `  `# initializing list ` `test_list ``=` `[``3``, ``5``, ``1``, ``6``, ``7``, ``9``] ` ` `  `# printing original list ` `print` `(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# using sum()+ map() ` `# to get count of elements matching condition  ` `# checks for odd ` `res ``=` `sum``(``map``(``lambda` `i: i ``%` `2` `!``=` `0``, test_list)) ` ` `  `# printing result ` `print` `(``"The number of odd elements: "` `+` `str``(res)) `

Output :

```The original list is : [3, 5, 1, 6, 7, 9]
The number of odd elements: 5
```

Method #3 : Using `reduce() + lamda`
reduce function does the task of accumulation as the sum function in the above used methods. lambda is used to perform the condition against which result needs to be checked.

 `# Python 3 code to demonstrate  ` `# to get count of elements matching condition  ` `# using reduce() + lambda ` ` `  `# initializing list ` `test_list ``=` `[``3``, ``5``, ``1``, ``6``, ``7``, ``9``] ` ` `  `# printing original list ` `print` `(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# using reduce() + lambda ` `# to get count of elements matching condition  ` `# checks for odd ` `res ``=` `reduce``(``lambda` `count, i: count ``+` `(i ``%` `2` `!``=` `0``), test_list, ``0``) ` ` `  `# printing result ` `print` `(``"The number of odd elements: "` `+` `str``(res)) `

Output :

```The original list is : [3, 5, 1, 6, 7, 9]
The number of odd elements: 5
```

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