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Machine learning engineering, starting from zero

You have never written a line of code. By the end you will have built something that makes predictions, put it where other people can use it, and be able to say who it gets wrong. Twenty-seven steps. Each one adds exactly one new thing.

About 95 hoursAny laptopNothing to pay7 of 27 steps built so far
First, the obvious question

What is a machine learning engineer?

Every day a computer decides something about a person. Whether your card payment goes through. Which ten of four hundred job applications a human ever reads. Whether a scan gets looked at today or in three weeks.

Nobody sat down and wrote those rules by hand. Somebody showed a computer a large pile of past cases and let it work out its own rules. That is machine learning. The set of rules it works out is called a model.

A machine learning engineer is the person who does that. Then they do the harder part, which is the part most courses never mention.

Far more people can do the second one than can do all five. That gap is where the work is.

Since you are going to ask

The job title to search for is machine learning engineer. In the United Kingdom, Indeed puts the average at £76,198 a year, from 811 salaries reported, updated in May 2026.

Read that honestly. It is an average across everybody in the role, including people with ten years behind them. A first job pays a good deal less than that, and this course does not promise you one. It is here so you can look the number up yourself rather than take a stranger's word that the work exists.

A tasteTwo minutes

One minute out of the first day

Here is a real piece of the first step. It uses a table of 4,521 phone calls a bank made to its customers. Think of a spreadsheet: 4,521 lines, one per call.

One of the columns says how many days ago the bank last called that person. You want the average.

Below, the grey boxes are the instructions you type. df is just the name we give the table. print means show me on screen, not on paper.

Step 0 · The table is not the truth

You ask for the average. This is the whole of it, one line.

print(round(df["pdays"].mean(), 2))

On screen 39.77

About 40 days. That sounds about right. So you look at the smallest value in the column.

print(df["pdays"].min())

On screen -1

Nobody was called minus one days ago. So you count how many lines say that. The .sum() on the end is what turns it into a count.

print((df["pdays"] == -1).sum())

On screen 3705

The notes that came with the file say minus one means the bank had never called that person before. So 3,705 of your 4,521 lines are not a number of days at all.

Your 39.77 was 816 real day counts and 3,705 non-days, added up and divided by everything. The true figure, for people who really had been called before, is 224.87.

Nothing warned you. It printed. It had two decimal places. It looked exactly like every number you have ever trusted.

Now here is the question you have to answer to pass that step.

The question that decides step 0

Your file has 4,521 lines. You print the average of pdays and get 39.8. Then you find that 3,705 of those lines hold minus one, and the notes say minus one means the person was never called before. What was your 39.8? Say what it is an average of.

You could very nearly answer that already, having read one page. That is the whole design. You are never told a thing is true. It happens to you, on your own screen, and then you never need telling again.

Practicalities

What you are actually doing, for ninety-five hours

Fair question, and most course pages never answer it.

Where the typing happens

You install two free things on your own laptop. One is called Python. It is a language for writing instructions a computer follows, in order, from the top. A list of instructions like that is a program.

The other gives you a notebook. Not a paper one. It is a page on your screen, split into boxes. You put instructions in a box, press two keys, and the answer appears underneath that box. That is where you spend most of the ninety-five hours.

Nothing you install will slow your laptop down, and all of it can be removed again.

What a mark out of one means

You will see numbers like 0.88 everywhere. That is a mark, and it counts out of one instead of out of a hundred. So 0.88 means it got 88 right out of every 100.

A large part of this course is about why that number tells you far less than it looks like it does.

You bring your own data on day one

In step 0 you go and find a table about something you actually care about. Your work, your town, your football team, your shop. It comes with you through all twenty-six steps after that, so everything you learn gets done twice: once on mine, once on yours.

That is the difference between finishing this and not finishing it.

When you get stuck at eleven at night

You will. Everybody does. So every single step where something is likely to go wrong has a box attached to it, right there, saying what that message means and what to do next.

The setup page ends by having you misspell a word on purpose, so you see red text, read it, and fix it while nothing is at stake. Getting used to errors early is most of what separates people who keep going from people who stop.

How long that is in real life

Ninety-five hours is two evenings a week for about a year, or five weeks of full days. It is not a weekend and I would rather say so on the front page.

Honesty

Is this for you, and where the course actually is

Yes, if

  • You have never written a line of code and nobody has ever shown you.
  • You can use a laptop for email and documents. That is the bar.
  • You want to change what you do for a living, or there is data at work nobody is using.
  • You would rather understand one thing properly than half understand ten.

Not really, if

  • You want this in a weekend. It is about ninety-five hours, and the seven steps that exist run to about twenty-seven.
  • You want a certificate more than the skill. There is no certificate.
  • You are after the AI that writes text or makes pictures. This is the other kind, the quiet kind that runs inside banks, hospitals and shops.
  • You already build models for a living. Start at step 16.

Where the course is today, said at the front rather than the back

Seven of the twenty-seven steps are finished. The setup page is finished. The other twenty are not started. That is about twenty-seven hours of real work and a plan for the rest.

They are deliberately not started. One step, put in front of a real beginner, tells you whether the whole shape works. Twenty-seven half-built ones tell you nothing, and cost twenty-seven times as much to fix.

So: the six that exist are finished properly and you can judge them today. If you need a complete course this month, this is not it yet, and you should know that before you spend an hour installing anything.

Do I need maths?

No. Nothing here is derived from first principles and there are no equations to learn. The hardest sum in the course is four numbers taken away from four other numbers, on paper, in step 12. If you can work out a tip you have enough.

What it does not cover, plainly

No image generators, no chatbots, no writing tools. No cloud exam. You will finish ready to begin studying for one of those exams, which is not the same as holding one, and I would rather say that now than let you find out later.

What you need

How it works

Every step is the same shape

After the first one you always know what is coming, so your attention goes on the new thing instead of on the format.

PredictWrite down what you think will happen, before anything runs.
RunRun working instructions somebody else wrote. Watch them.
InvestigateTake them apart. Say why they are written that way.
ModifyChange one named thing, and predict again.
MakeBuild your own, on your own data, with no answer given.
CheckSix questions. One of them decides whether you passed.

Every step ends with something you can hold

A tree drawn on paper. A grid of your model's mistakes, printed and stuck on a wall. A short video of somebody else using the thing you built. A number on a screen is not something you can show anybody.

There is no failing

A step is passed, or it is not yet. Not yet always comes with the one thing that would change it. Four things are asked for every time, and a step adds one or two of its own. The list at the foot of each step is the one that counts.

  1. The thing you built, and it still works when somebody else runs it.
  2. A written log naming one thing that broke, and one guess you got wrong.
  3. Five of the six check questions right, including the one that counts.
  4. Ninety seconds of you, out loud, pointing at one decision and saying why it is there.

That last one is a job interview. Doing it after every step is how it stops being frightening.

Working on your own

Nothing here needs another person. The trick that works: put your work away for a day, come back to it cold, and write down what a stranger would ask you.

It is still better with one friend doing it in the same week. That costs nobody anything.

The ladderTwenty-seven steps

What you learn, in order

Five parts. If you read only the five headings and the paragraph under each, you will know what this course is.

Part one · Steps 0 to 7

Look at data without being fooled by it

You take a real messy file, work out what is wrong with it, get it into a shape a computer can use, invent the missing columns, and build something that predicts. Most of the job is in this part, and most courses skip straight past it.

  • 0The table is not the truth. Find what is wrong with real data. Choose your own table.Ready
  • 1A rule you wrote yourself. Predict by hand, and find out whether guessing would have done better.Ready
  • 2Rules the computer works out. Your first model, small enough to draw on paper. It picks the same rule you did, and then you find out why that is less impressive than it looks.Ready
  • 3Cheating, on purpose. Your almost perfect tree scores 0.7975 on people it has never seen, which is worse than saying no to everybody. Then you build three better lies on purpose.Ready
  • 4Getting the file into a usable shape. Nine columns of words become 41 columns of numbers, the model finds October on its own, and you learn how to tell whether a win that size is real.Ready
  • 5Making columns that were not there. Two dates become the gap between them, and one question beats twenty. Then four sensible columns for the bank file, and not one of them pays.Ready
  • 6Which columns are pulling their weight. A column holding nothing but the row number comes third out of forty-eight, and the ranking that catches it still cannot catch a cheat.Ready
  • 7Marking it properly, and who pays. Make your model more willing to say yes, then look at whose lives just got worse.
Part two · Steps 8 to 15

Six kinds of model, and when each one is wrong

Six kinds of model, one per step, and then two steps on choosing between them honestly. Anybody can run a model. The skill is knowing which one to reach for, and the job each one quietly fails at.

  • 8Predicting a number instead of a yes or no. How much, not whether.
  • 9Answering with a chance. Not yes, but seven times in ten. And what that does not mean.
  • 10Guessing from whoever is most similar. No rules at all, just the nearest matches.
  • 11Many poor guesses beat one good one. Eight hundred people guess the weight of an ox, and the average is almost exactly right.
  • 12Learning from your own mistakes. Four numbers on a page and no maths. The one that usually wins.
  • 13When nobody tells you the answers. Sorting things into groups when nothing is labelled, and the trap of always finding as many groups as you asked for.
  • 14Trying forty things without kidding yourself. Because forty attempts at one test is not one test.
  • 15Wrapping it so it cannot cheat. Then saving the whole thing, and running one new person through it.
Part three · Steps 16 to 19

Data in the state it really turns up in

Nobody hands you a tidy file. It is locked inside a company system, it has dates in it, it is written in sentences, and somebody in a meeting wants you to explain what the thing decided.

  • 16Fetching the data yourself, with SQL. Most of the time it lives in a company system, and SQL is how you ask it for what you want.
  • 17Yesterday's model is wrong today. Once your rows are in date order, the usual way of testing becomes a lie.
  • 18Working with writing, not numbers. Real sentences you collected, and the one word your model wrongly leans on.
  • 19Explaining it to somebody who will not take your word. Change one thing about one person and watch the answer flip.
Part four · Steps 20 to 24

Off your laptop and into something that runs on its own

This is the part that turns somebody who can build a model into somebody who gets paid to run one. It is also the part almost no beginner course goes near.

  • 20Out of the notebook, into proper files. Work another person can read and run without you.
  • 21Checks that catch it when it breaks. Including the ones that watch your data, not just your instructions.
  • 22Something other software can ask. And what your model says when it is asked about somebody unlike anyone it has seen.
  • 23Running somewhere that is not your laptop. Packed up so it still behaves the same in six months.
  • 24Watching it once it is out there. How you find out it has gone wrong, and when to rebuild it.
Part five · Steps 25 and 26

Getting hired

Treated as a skill you practise, not a thing you hope for.

  • 25Your own problem, start to finish. Your data, a real person who wants it, and five promises you made before you began.
  • 26What to show an employer, and the test they set. Most first tests are: here is one file, here is another, send us your answers. You will have done it before.
Trust

Every number on these pages was run, not remembered

When a page tells you that you should see 39.77, that is not somebody remembering. A small program works it out from the data and then checks that the same number is still written on the page. If the two ever disagree, the page is treated as broken and does not go out.

Those checks come with the course. You can run them yourself.

199numbers in the steps, checked against the real data
0errors nobody meant to leave in
12automatic checks a page must pass to go out
7 of 27steps finished

Every finished page is handed to a reviewer whose only job is to hunt one kind of fault in it and nothing else. Step 2 went through two of those before it went up, and one of them found that the course never installed the library Step 2 needs. The faults still outstanding are written down in the open, in the notes that come with the course, because a list of known faults is worth more to you than a claim there are none.

Begin

Where to start

Seven steps are finished. Together they are about twenty-seven hours, and they take you from opening a file to a model trained on every column the file has, and to knowing how much of the number under it you are entitled to believe.

  1. Read step 0 first, before installing anything. It costs you ten minutes and shows you exactly what a step looks like. If it does not grip you, nothing after it will.
  2. Then get your laptop ready. About an hour, once. It assumes you have never installed anything in your life, and it ends with you causing an error on purpose and reading it.
  3. Then step 1, where you build a rule by hand and find out what it was worth.
  4. Then step 2, where the computer works out its own rule and picks the same one you did.
  5. Then step 3, where you find out that the score you were so pleased with was measured on the wrong people.
  6. Then step 4, where every column of words becomes numbers, and you learn how to tell a result from a coincidence.
  7. Then step 5, where you build the column a model could never work out for itself, and then find out how seldom that is worth doing.
  8. Then step 6, where you ask the model which of its columns did the work, and learn how much of that answer to believe.

Or look at the raw material first

Moro, S., Laureano, R. and Cortez, P. (2011). Using Data Mining for Bank Direct Marketing. Proceedings of the European Simulation and Modelling Conference, 117-121. EUROSIS. · Salary figure: Indeed UK, machine learning engineer, 811 salaries reported, updated 10 May 2026.