Python videos | Python Part 3 - Ranges, loops and formatting

Posted by Andy Brown on 05 September 2021


This video explains how to create loops which execute while a particular condition is true (and how to break out of these loops), how to print messages more neatly and how to use ranges to loop over sequences of numbers.

See our full range of Python training resources, or test your knowledge of Python with one of our Python skills assessment tests.

This video has the following accompanying files:

File name Type Description
List even squares.py Python code Using a while loop to list out the first N even squares
Fizz buzz.py Python code Listing out the first N numbers divisible by 3
Greet pets.py Python code Using variables when printing to greet cats by name
List math terms.py Python code Listing out cubes and reciprocals nicely formatted
Range syntax.py Python code Syntax of range with one to three arguments
Range example.py Python code Using range to list out the first N cubes
Prime numbers.py Python code Nested ranges listing out prime numbers

Click to download a zipped copy of the above files.

After watching this video, you may like to test your understanding by doing one or more of the following exercises:

Exercise Level
Use the range and format functions to loop down from 10 to 1 displaying a countdown message Easy
Use the range and format functions to list the square roots of the first 100 integers Standard
Use the range function in an outer loop to find all the primes up to 100 using an inner loop Standard
Print out ever-more-accurate estimates of the value of pi using the Leibniz series Hard

You can also download the answers to each exercise from the links above.

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This page has 1 thread Add post
Surendra7   Reply to Surendra7Reply
19 Dec 21 at 16:00

Does changing the range for prime test to 

for possible_prime in range(2,int(test_number/2)):

will make code more effiecient.

Andy B   Reply to Andy BReply
20 Dec 21 at 09:27

The algorithm given is to teach Python, and doesn't claim to be efficient.  A simple improvement would be to test from 2 up to the square root of the possible prime, rather than half of it, on the grounds that two factors of a prime can't both be greater than its square root, otherwise when you multiplied them together you'd get a number greater than the prime.  There are many better tests for primeness than this, though.

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