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Coding Grandmaster from scratch.

Coding Grandmaster is for learners who know Python basics and want to understand how the clever parts work. Instead of importing libraries, you build them: a sieve, a sorting counter, Bayes' rule, a regression line, a nearest-neighbour classifier and a small neural network, one short project at a time.

Start lesson 1Your certificate

46 lessons

What you will do

1. Algorithms and speed

1

How fast is it? Counting steps

Write pair_checks(n): two nested loops that count every pair (i, j) with i smaller than j among n items, and return the count. The program prints pair_checks(10).

Start →2

Searching one by one

Write find(items, target) that returns a pair (index, comparisons). If the target is missing, the index is -1 and the comparisons equal the length of the list.

Start →3

Halving the search

Write binary_search(items, target) for a sorted list. Return (index, steps) where steps counts how many middle items you looked at, or (-1, steps) if it is missing.

Start →4

Two ways to sort

Write bubble_sort(items) and selection_sort(items). Each returns (sorted_list, swaps) and must not change the list it was given. The program prints both results for the list.

Start →5

The growth race

For each size in the list print one line like n=10 linear=10 nlogn=33 quadratic=100, where nlogn is int(n * math.log2(n)).

Start →6

Remembering answers

Write fib_naive(n) returning (value, calls) and fib_memo(n, memo) returning the value while counting calls in memo["calls"]. Print the results for 20.

Start →

2. Number magic

7

Euclid's shortcut

Write gcd_steps(a, b) returning (gcd, steps) where steps counts the remainder steps, and lcm(a, b). Print gcd_steps(48, 18) and lcm(4, 6).

Start →8

The sieve of Eratosthenes

Write primes_below(n) using a list of True/False flags (a sieve) that returns the list of primes less than n. Print how many primes there are below 100 and the last one.

Start →9

Digits and casting out nines

Write digit_sum(n) using % and //, and digital_root(n) that repeats digit_sum until one digit remains. Print both for 98765.

Start →10

Powers in a flash

Write power_steps(base, exp) that returns (result, multiplications) using repeated squaring, and pow_mod(base, exp, m) that returns base ** exp % m the same way (without ever building the full power).

Start →11

Perfect numbers

Write divisor_sum(n) (the sum of proper divisors, found by looping d up to the square root and adding both d and n // d) and print the perfect numbers below 1000.

Start →12

Counting in other bases

Write to_base(n, base) returning the digits as text, using the string "0123456789ABCDEF". Print 10 in binary and 255 in hexadecimal.

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3. Bit play

13

Seeing the bits

Print each of 5, 12 and 255 as 8 binary digits, and write count_ones(n) that counts the 1 bits using & and >>.

Start →14

One-line bit tricks

Write is_power_of_two(n) using n & (n - 1), is_odd(n) using n & 1, and print the powers of two up to 200 using a list comprehension.

Start →15

XOR magic

Swap a and b with three XOR lines (no temporary variable), and write lonely(numbers) that returns the number that appears only once by XOR-ing everything together.

Start →16

Set, clear and toggle

Write set_bit(n, i), clear_bit(n, i), toggle_bit(n, i) and test_bit(n, i) (True or False) using shifts and bitwise operators.

Start →17

Every subset

Write subsets(items) returning a list of every subset as a list, in the order of the counter 0 to 2^n − 1, using bit tests. Print how many subsets four items have, and the subsets of two items.

Start →18

Permission flags

With READ = 4, WRITE = 2 and EXEC = 1, write grant(perms, flag), revoke(perms, flag), has(perms, flag) and describe(perms) which returns text like r-x (r, w and x, or - for a missing one).

Start →

4. Probability

19

Counting outcomes

Write ways(target), the number of dice pairs that add up to target, and as_fraction(top, bottom) that returns text like 1/6 in lowest terms. Print the chance of a total of 7.

Start →20

The OR rule

Build the 52-card deck as (rank, suit) pairs, then count the cards that are the chosen suit, the chosen rank, both, and either. Print the four counts and the chance of either as a fraction in lowest terms.

Start →21

Given that…

For the chosen club print how many students are in it, how many passed, and P(passed | club) as a percentage with one decimal place. Then print P(passed) for all students.

Start →22

Bayes and the medical test

Write posterior(prior, sensitivity, specificity) returning P(sick | positive) rounded to 4 decimal places. Print it for prior 0.01, sensitivity 0.9, specificity 0.9.

Start →23

The binomial distribution

Write binomial(n, k, p) and use it to print the chance of exactly 3 heads in 5 fair flips, the chance of at least 4 heads, and the total of all the chances (rounded to 6 places).

Start →24

How computers fake randomness

Write next_value(seed) with that formula, and roll(seed) = 1 + seed % 6. Starting from the given seed, roll 600 times (feeding each result back in) and print how many times each face 1 to 6 came up.

Start →

5. Statistics

25

Averages

Write mean(data), median(data) and mode(data). If several values tie for most common, mode returns the smallest of them. Print all three for the list.

Start →26

How spread out?

Write data_range(data), variance(data) and std_dev(data) (population versions, dividing by n). Print them for the data, rounding the standard deviation to 4 decimal places.

Start →27

Quartiles and outliers

Write quartiles(data) returning (q1, q2, q3) by the method above, and outliers(data) returning the sorted list of outliers by the 1.5 × IQR rule.

Start →28

A histogram in text

Count how many students got each grade and print one line per grade in alphabetical order, like A | #### 4.

Start →29

Do two things move together?

Write correlation(xs, ys) that returns Pearson's r rounded to 4 decimal places. Print it for study hours against marks.

Start →30

Scaling and z-scores

Write min_max(values) and z_scores(values) (use the population standard deviation). Both return lists with each number rounded to 2 decimal places.

Start →

6. Data science from scratch

31

Records, filters and rankings

Keep the students whose score is at least cutoff, sort them by highest score (ties by name), print how many qualified, and print the first top of them as a numbered list.

Start →32

Group by: totals per region

For every sale of at least minimum, add it to its region. Print one line per region (alphabetical) like east: total 360, average 180.0, orders 2.

Start →33

Cleaning messy data

Write fill_missing(values) that replaces each None with the mean of the other values rounded to 1 decimal place, and remove_duplicates(values) that keeps only the first of each repeated value in order. Print both results for the readings.

Start →34

Draw a bar chart

Draw one filled bar for each value, 40 wide and 15 times the value tall, 50 apart, starting at x = -150 along the line y = -100, using a different colour from the list for each.

Start →35

Draw a line chart

Draw an x axis and a y axis from the origin at (-150, -100), then plot the sales as dots (50 apart across, 5 times the value up) joined by lines.

Start →36

Capstone: a report table

Write grade(score) (A for 80 or more, B for 70 or more, otherwise C) and print the ranking, highest first, as an aligned table with a header, then the average (2 decimal places) and the name of the top scorer.

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7. Machine learning from scratch

37

Predictions and error

Write predict(x, m, b) and mse(xs, ys, m, b). Print the prediction for each size and the mean squared error of the line with the given m and b, rounded to 2 decimal places.

Start →38

Training by searching

Try every m from 0 to 100 in steps of 5 and every b from 0 to 200 in steps of 10 with the same data. Print the best m, the best b and their error rounded to 2 decimal places.

Start →39

Gradient descent

Starting from m = 0, repeat steps times: compute the gradient, then do m = m - lr * gradient. Print the final m rounded to 4 decimal places and the final mean squared error rounded to 4.

Start →40

The straight-line formula

Compute the slope and intercept with these formulas, print them rounded to 3 decimal places, and print the prediction for new_x rounded to 2 places.

Start →41

Classifying by neighbours

Write classify(point, train, k): sort the training examples by distance to the point, take the k closest, and return the label that appears most among them (if tied, the label of the nearest one).

Start →42

A perceptron learns AND

Train a perceptron on the AND truth table starting from zero weights, for the number of epochs, with each update using a learning rate of 1. Print the final weights and bias as w1 w2 b, then the four predictions.

Start →

8. Neural networks from scratch

43

A single neuron

Write sigmoid(z) and neuron(inputs, weights, bias) which returns the sigmoid of the weighted sum plus the bias. Print the neuron's output, rounded to 4 decimal places, for each input pair.

Start →44

A two-layer network

Write forward(x1, x2) for a network with two hidden neurons and one output neuron, using the given weights, and print the output rounded to 3 decimal places for the four input pairs.

Start →45

Teaching a neuron OR

Train a neuron on the OR table, starting from weights 0.1, -0.1 and bias 0, for 1,000 epochs with learning rate lr. Print the four outputs rounded to 2 decimal places.

Start →46

Why XOR needs a hidden layer

Write step(z) and xor_net(a, b) using two hidden neurons, h1 = step(a + b - 0.5) and h2 = step(a + b - 1.5), and the output step(h1 - h2 - 0.5). Print the XOR table, one line per row, like 0 1 -> 1.

Start →

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FAQ

Coding Grandmaster: questions

What will I learn in Coding Grandmaster?

You will build algorithms, probability and statistics tools, a data report with charts, and machine-learning models from scratch in Python, understanding each step. Each of the 46 lessons has one small task and automatic checking.

How long does it take?

About 690 minutes in total, 46 short lessons of around 15 minutes each. Go at your own pace.

Do I need to know anything first?

Yes: you should be comfortable with Python basics, meaning variables, loops, lists and functions. The free Learn Python course covers exactly that.

Do I get a certificate?

Yes. Finish all the lessons and you can download a free certificate of completion with your name. It is a record of what you did, not an accredited qualification.

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