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Learn Python 3 Fundamentals

Solution Review: Highs and Lows

Explore how to use Python's filter function with lambda expressions and list comprehensions to categorize numbers in lists. Understand step-by-step code explanations for counting elements based on conditions using data structures in Python.

We'll cover the following...

We’ll discuss two solutions to this problem.

Solution 1: Using filter and lambda

Let’s explore the first solution to the problem of highs and lows:

Python 3.10.4
def count_low_high(num_list):
    if (len(num_list)==0):
        return None
    high_list = list(filter(lambda n: n > 50 or n % 3 == 0, num_list))
    low_list = list(filter(lambda n: n <= 50 and not n % 3 == 0, num_list))
    return [len(low_list), len(high_list)]
num_list = [20, 9, 51, 81, 50, 42, 77]
print(count_low_high(num_list))

Explanation

Here’s a line-by-line explanation of the code for the problem highs and lows:

  • Line 1: Defines a function named count_low_high that takes one argument num_list, which is expected to be a list of numbers.

  • Line 2: Checks if the length of num_list is zero, meaning the list is empty.

  • Line 3: If the list is empty, the function returns None.

  • Line 4: Creates a list named high_list by ...