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# Python – Test for strictly decreasing list

• Last Updated : 10 Aug, 2022

The test for a 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 sequences can be useful to gather knowledge. Let us 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 the beginning and list beginning from the first element, so that a check can be performed on all elements.

## Python3

 `# 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.

## Python3

 `# 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```

Method #3 : Using sort() and extend() methods

## Python3

 `# Python3 code to demonstrate``# to check for strictly decreasing list` `# initializing list``test_list ``=` `[``10``, ``8``, ``7``, ``5``, ``4``, ``1``]` `# printing original lists``print` `(``"Original list : "` `+` `str``(test_list))` `# to check for strictly decreasing list``res``=``False``x``=``[]``x.extend(test_list)``test_list.sort(reverse``=``True``)``if``(x``=``=``test_list):``    ``res``=``True``# 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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