Python – Custom Lower bound a List

Given a list, assign a custom lower-bound value to it.

Input : test_list = [5, 7, 8, 2, 3, 5, 1], K = 3 
Output : [5, 7, 8, 3, 3, 5, 3] 
Explanation : All elements less than 3, assigned 3.

Input : test_list = [5, 7, 8, 2, 3, 5, 1], K = 5 
Output : [5, 7, 8, 5, 5, 5, 5] 
Explanation : All elements less than 5, assigned 5. 

Method #1: Using list comprehension

In this, we check for each element if it’s lower than lower-bound, if yes, then assign the decided lower-bound to that element.

Python3

# Python3 code to demonstrate working of
# Custom Lowerbound a List
# Using list comprehension

# initializing list
test_list = [5, 7, 8, 2, 3, 5, 1]

# printing original list
print("The original list is : " + str(test_list))

# initializing Lowerbound
K = 4

# checking for elements and assigning Lowerbounds
res = [ele if ele >= K else K for ele in test_list]

# printing result
print("List with Lowerbounds : " + str(res))

Output

The original list is : [5, 7, 8, 2, 3, 5, 1]
List with Lowerbounds : [5, 7, 8, 4, 4, 5, 4]

Time Complexity: O(n)
Auxiliary Space: O(n)

Method #2 : Using list comprehension + max()

In this, we perform comparison using max(), assign max of the element, or the lower-bound as decided.

Python3

# Python3 code to demonstrate working of
# Custom Lowerbound a List
# Using list comprehension + max()

# initializing list
test_list = [5, 7, 8, 2, 3, 5, 1]

# printing original list
print("The original list is : " + str(test_list))

# initializing Lowerbound
K = 4

# max() is used to compare for Lowerbound
res = [max(ele, K) for ele in test_list]

# printing result
print("List with Lowerbounds : " + str(res))

Output

The original list is : [5, 7, 8, 2, 3, 5, 1]
List with Lowerbounds : [5, 7, 8, 4, 4, 5, 4]

Time Complexity: O(n) where n is the number of elements in the list “test_list”.  This is because we’re using the built-in list comprehension + max() which all has a time complexity of O(n) in the worst case.
Auxiliary Space: O(1), no extra space is required