# Python – Test for strictly decreasing list

• Last Updated : 29 Dec, 2019

The test for monotonic sequence is a utility that has manifold applications in mathematics and hence every sphere related to mathematics. As mathematics and Computer Science generally go parallel, mathematical operations such as checking for strictly decreasing sequence can be useful to gather knowledge of. Lets discuss certain ways to perform this test.

Method #1 : Using `all() + zip()`
The all() generally checks for all the elements fed to it. The task of zip() is to link list beginning from beginning and list beginning from first element, so that a check can be performed on all elements.

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 `# Python 3 code to demonstrate ``# Test for strictly decreasing list``# using zip() + all()`` ` `# initializing list``test_list ``=` `[``10``, ``8``, ``7``, ``5``, ``4``, ``1``]`` ` `# printing original lists``print` `(``"Original list : "` `+` `str``(test_list))`` ` `# using zip() + all()``# Test for strictly decreasing list``res ``=` `all``(i > j ``for` `i, j ``in` `zip``(test_list, test_list[``1``:]))`` ` `# printing result``print` `(``"Is list strictly decreasing ? : "` `+` `str``(res))`
Output :

```Original list : [10, 8, 7, 5, 4, 1]
Is list strictly decreasing ? : True
```

Method #2 : Using `reduce()` + lambda
reduce() coupled with lambda can also perform this task of checking for monotonicity. reduce function is used to cumulate the result as True or False, lambda function checks for each index value with next index value.

 `# Python 3 code to demonstrate ``# Test for strictly decreasing list``# using reduce() + lambda`` ` `# initializing list``test_list ``=` `[``10``, ``8``, ``7``, ``5``, ``4``, ``1``]`` ` `# printing original lists``print` `(``"Original list : "` `+` `str``(test_list))`` ` `# using reduce() + lambda``# Test for strictly decreasing list``res ``=` `bool``(``lambda` `test_list: ``reduce``(``lambda` `i, j: j ``if` `i > j ``else` `9999``, test_list) !``=` `9999``)`` ` `# printing result``print` `(``"Is list strictly decreasing ? : "` `+` `str``(res))`
Output :
```Original list : [10, 8, 7, 5, 4, 1]
Is list strictly decreasing ? : True
```

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