Python Principles Challenges

This week I decided to test my skills and try to complete all the free challenges from python principles.

https://pythonprinciples.com/challenges/

After a lot of attempts and bug-fixing, I have solved all of them. :)

These challenges were especially rewarding as they contained new concepts that I was forced to research and learn myself. Below I showcase some of the examples I completed.

Custom zip

The built-in zip function "zips" two lists. Write your own implementation of this function.

My code:

def zap(a, b):
    return[(a[x], b[x]) for x in range(len(a))]

print(zap(
    [0, 1, 2, 3],
    [5, 6, 7, 8]
))

Output: [(0, 5), (1, 6), (2, 7), (3, 8)]

The function takes 2 lists and combines the corresponding items into a tuple. This was quite challenging for me as one of the conditions was - the function can only contain one line.

Thousands seperator

Write a function that converts a number to a string and adds commas as a thousands separator.

My code:

def format_number_1(num):  # Function takes a single parameter 'num'
    string = str(num)[::-1]  # Uses string slicing to reverse the number
    count = 0
    for x in range(len(string)):  # Iterates through each letter
        if x !=0 and (x % 3) == 0:  # Conditions pass every 3 letters
            string = string[:x + count] + "," + string[x + count:]  # adds comma to string using splits
            count += 1
    return string[::-1]  # Reverses the number again to give output

When the function is called with the number: '4591534516'

It returns: '4,591,534,516'

This was by far the hardest challenge, taking more time than all the others combined. In the end I reached a solution I am very happy with, however, I now know it can be done like this:

def format_number(num):
    return "{:,}".format(num)

I learnt quite a bit more doing it manually than by using the built in .format() function so I am glad I spent the time to work through it.