# Python | Matrix True Summation

• Last Updated : 27 Feb, 2020

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 like in data Science. Lets discuss certain ways in which we can count True values in Matrix.

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 ``# Matrix True Summation``# using sum() + generator expression ``from` `itertools ``import` `chain`` ` `# initializing list ``test_list ``=` `[[``3``, ``False``], [``False``, ``6``], [``False``, ``9``]] `` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list)) `` ` `# using sum() + generator expression ``# Matrix True Summation``res ``=` `sum``(``1` `for` `i ``in` `chain.from_iterable(test_list) ``if` `i ``=``=` `True``) `` ` `# printing result ``print` `(``"The number of True elements: "` `+` `str``(res)) `

Output :

```The original list is : [[3, True], [True, 6], [True, 9]]
The number of True elements: 3
```

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 ``# Matrix True Summation``# using sum()+ map() ``from` `itertools ``import` `chain`` ` `# initializing list ``test_list ``=` `[[``3``, ``True``], [``True``, ``6``], [``True``, ``9``]] `` ` `# printing original list ``print` `(``"The original list is : "` `+` `str``(test_list)) `` ` `# using sum()+ map() ``# Matrix True Summation``res ``=` `sum``(``map``(``lambda` `i: i ``=``=` `True``, chain.from_iterable(test_list))) `` ` `# printing result ``print` `(``"The number of True elements: "` `+` `str``(res)) `

Output :

```The original list is : [[3, True], [True, 6], [True, 9]]
The number of True elements: 3
```

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