F02

Programming 1: Thinking in Steps

“Writing a recipe a robot follows *exactly*”

Your first recipe for a computerA program is a list of instructions the computer follows exactly, top to bottom. print() shows text on screen. · 10 min
Values, types and arithmeticEvery value in Python has a type (whole number, decimal, text, true/false), and the type decides what you can do with it. · 12 min
Variables: names for valuesA variable is a name tag stuck on a value so you can use it later. The = sign means "stick this name on that value", not "is equal to". · 12 min
Talking to the userinput() asks the user a question and always gives back text. Convert it with int() or float(), and build answers with f-strings. · 12 min
Making decisionsif, elif and else let a program choose what to do. Conditions are True/False questions built with comparisons and and/or/not. · 14 min
Repeating with whileA while loop repeats a block of code as long as a condition stays True. Something inside the loop must eventually make it False. · 13 min
for loops and rangeA for loop does something once for each item in a sequence. range() makes a sequence of numbers, and an accumulator builds up a result. · 14 min
Meet Bit the robotControl a robot on a grid with a handful of commands. Sequences, loops and decisions turn a few simple commands into smart behavior. · 15 min
Functions: your own instructionsdef creates a new instruction with a name. Parameters are its inputs, and return sends a result back to whoever called it. · 15 min
Scope and the call stackEvery function call gets its own private workspace (a frame). Calls stack up like plates, and each one disappears when it returns. · 14 min
Decomposition and abstractionBig problems become easy when you split them into small, named helper functions. Each helper hides its details behind a clear name. · 16 min
Strings up closeA string is a sequence of characters you can index, slice, search and transform. Strings never change; methods give you new ones. · 16 min
ListsA list holds many values in order, under one name. You can index it like a string, but unlike a string you can change it. · 15 min
Mutability, aliasing and cloningTwo names can refer to the same list. Change it through one name and the other sees the change too. Copy the list when you want independence. · 15 min
Tuples and list comprehensionsA tuple is a list that can't change, perfect for fixed groups like coordinates. A list comprehension builds a whole list in one readable line. · 14 min
Grids and imagesA list of lists makes a grid. A digital image is exactly that, a grid of pixels, so with two nested loops you can write your own photo filters. · 18 min
Dictionaries and setsA dictionary looks things up by a label (key) instead of a position. A set keeps only unique items and answers "is it in here?" instantly. · 16 min
Reading and writing filesFiles let data outlive your program. Open a file, read it line by line or write to it, and Python closes it for you with a with block. · 15 min
When things go wrongErrors are Python's way of saying "I can't do this." try/except lets your program catch an error and recover, and raise lets you signal your own. · 14 min
Testing and debuggingTesting is trying your code on carefully chosen inputs to find bugs. Debugging is the detective work of finding why a bug happens, one experiment at a time. · 16 min
Floats and approximationComputers store most decimals only approximately, so 0.1 + 0.2 isn't exactly 0.3. Instead of exact answers, good programs find answers that are close enough, fast. · 16 min
Objects and classesA class is a blueprint for a new kind of value. Each object made from it bundles its own data (attributes) with the things it can do (methods). · 17 min
InheritanceA subclass is a more specific version of a class. It inherits everything from its parent and can add or change behavior. · 15 min
How fast is my code?Instead of timing code with a stopwatch, count how the number of steps grows as the input grows. That growth, written as Big-O, tells you whether code will still be fast with a million items. · 17 min
Drawing and plottingA canvas is a grid of pixels with (0, 0) at the top-left. Shapes, loops and a little math turn numbers into pictures and data into charts. · 15 min
Boss level: build a text adventurePut everything from this course together to build a playable game, with rooms in dictionaries, state in variables, commands parsed from strings, and functions keeping it organized. · 45 min

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