Check if List is Strictly Increasing - Python

We are given a list of numbers and our task is to check whether the list is strictly increasing meaning each element must be greater than the previous one. For example: a = [1, 3, 5, 7] this is strictly increasing and b = [1, 3, 3, 7], this is not strictly increasing as 3 appears twice.

Using all() with zip()

all() function checks if all conditions in an iterable are True and zip() pairs adjacent elements for comparison.

a = [1, 3, 5, 7]
res = all(x < y for x, y in zip(a, a[1:]))

print(res)  

True

Explanation:

• zip(a, a[1:]) pairs consecutive elements: (1,3), (3,5), (5,7).
• generator x < y ensures that each number is strictly less than the next.
• all(...) returns True only if all comparisons hold.

Using itertools.pairwise()

pairwise() function from itertools generates consecutive element pairs, making comparisons clean and efficient.

from itertools import pairwise  

a = [1, 3, 5, 7]
res = all(x < y for x, y in pairwise(a))

print(res)  

True

Explanation:

• pairwise(a) generates adjacent pairs: (1,3), (3,5), (5,7).
• all(x < y for x, y in pairwise(a)) checks if each element is less than the next.

Using a Loop

A for loop can be used to compare adjacent elements and check if they are strictly increasing.

a = [1, 3, 5, 7]
res = True  

for i in range(len(a) - 1):
    if a[i] >= a[i + 1]:
        res = False
        break  

print(res)  

True

Explanation:

• We iterate through the list using range(len(a) - 1), checking adjacent elements.
• If a[i] >= a[i+1], the sequence is not strictly increasing, so we set res = False and break the loop.

Using sorted()

We can check if the list is strictly increasing by comparing it with its sorted version and we sort the list using sorted().

a = [1, 3, 5, 7]
res = a == sorted(a) and len(set(a)) == len(a)

print(res)  

True

Explanation:

• sorted(a) returns a sorted version of a. If a is already sorted, the condition holds.
• len(set(a)) == len(a) ensures no duplicate elements, making it strictly increasing.

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Article Tags :

• Python
• Python Programs
• Python list-programs

Practice Tags :

• python