Python Basics

Code runs one instruction at a time. In this first lesson, the only thing we need to care about is how to send a message back to the screen.

print() is the simplest way to do that. It takes a value, turns it into something the computer can display, and then shows it on its own line. That makes it a useful starting point whenever you want to test an idea quickly.

print("A message for the person using the program")

Run this once before changing anything. Then replace the words between the quotation marks and notice that the structure of the program stays the same while the output changes.

print("Hello, I am Maya!")

Programs work with different kinds of information: text, whole numbers, decimals, and true-or-false values. The important part here is not just that these kinds exist, but that Python treats them differently.

When you see a value in code, it helps to ask two questions: what is the value, and what type of value is it? That habit becomes useful later when a piece of code behaves differently from what you expected.

"text"     # a string
42         # an integer
True       # a boolean

type() tells us what kind of value Python sees. This is one of the simplest debugging tools you can use when a result looks strange, because it shows whether Python is handling text, numbers, or a boolean.

print(type(3.14))

Variables give useful names to values, so we can use them again later. This is one of the main ideas in programming: instead of repeating the same thing over and over, give it a label and refer back to it.

Think of a variable as a label on a box. The label is what you write in code, and the value is what the label points to. When the value changes, the name stays the same unless you assign something new to it.

name = "Ada"
print(name)

Store two details, then print them together. This shows that a program can combine separate pieces of information into one sentence or one result.

city = "Lagos"
print(city)

Strings are text, and text is the easiest place to start practicing with real program output. Once you can store and change text, you can build prompts, labels, messages, and user-facing responses.

F-strings let us place a variable directly inside a sentence. They are useful because they keep the final message readable without needing to join many small pieces together.

name = "Sam"
message = f"Welcome, {name}!"

Use a string method to change text to uppercase. Methods are little actions attached to a value, and this is your first chance to see how Python can transform text without replacing the original idea.

food = "pizza"
print(food.upper())

Lists keep ordered items together. They are useful when the order matters, when you want to walk through several values, or when you want to add and remove items over time.

The first item has position 0, which can feel strange at first. That numbering choice is common in programming, so it is worth getting comfortable with it early.

colors = ["red", "blue"]
first_color = colors[0]

Add an item to the end of a list with append(). This is a common pattern when you are collecting results step by step instead of writing the whole list at once.

animals = ["cat", "dog"]
animals.append("otter")
print(animals)

Dictionaries store related values under descriptive keys instead of positions. This makes them a strong fit when you already know the name of the thing you want and do not want to count through a list to find it.

You can think of a dictionary like a small lookup table. The key is what you ask for, and the value is what you get back.

profile = {"name": "Maya"}
print(profile["name"])

Add a new key and value to a dictionary. This shows that dictionaries are not fixed structures; you can expand them as your program learns more information.

book = {"title": "Dune"}
print(book["title"])