Edna's Python Archives

What this creature is

A variable is a name you give to a value stored in memory. You assign a value with = and can use that name later in your program.

Why you will regret ignoring it

Variables let you reuse values, update them, and keep your code readable. Without them, you would repeat the same literals everywhere.

Example

name = "Alex"
age = 20

Common disgrace

Using the same variable name for different things in one program, then getting confused when the value is not what you expect.

Trial by code

Create two variables: one for a word (string) and one for a number. Print both on one line.

What this creature is

A string is text inside quotes (single or double). It can include letters, digits, spaces, and symbols.

Why you will regret ignoring it

Most user-facing data is text. Python uses strings for names, messages, and anything you read or type as words.

Example

greeting = "Hello, world."
print(greeting)

Common disgrace

Starting a string with one kind of quote and ending with another, or leaving a string unclosed, which causes a syntax error.

Trial by code

Store a short sentence in a variable. Print it and print its length using len(...).

What this creature is

An integer is a whole number (no decimal part). You use it for counting, indexing, and math where fractions are not needed.

Why you will regret ignoring it

List positions, scores, and loop counts are often integers. Mixing integers and floats on purpose is fine; mixing them by accident causes bugs.

Example

items = 3
total = items + 2

Common disgrace

Expecting division of two integers to behave like “real” division in every case — in Python 3, / gives a float; use // for integer division when you need it.

Trial by code

Set a variable to 10, subtract 3, and print the result.

What this creature is

A float is a number with a decimal point. Use it for measurements, ratios, and any value that is not a whole number.

Why you will regret ignoring it

Many real-world values (money, science, graphics) need decimals. Floats are the usual way to represent them in Python.

Example

pi_approx = 3.14
half = 0.5

Common disgrace

Comparing two floats with == when they came from math operations — tiny rounding differences can make them not exactly equal.

Trial by code

Store two floats, multiply them, and print the result rounded to two decimal places.

What this creature is

A list is an ordered sequence in square brackets. Items have positions (indexes) starting at 0. You can add, remove, and loop over items.

Why you will regret ignoring it

Lists let one variable hold many values in order — for example, lines of text, scores, or names.

Example

words = ["variable", "string", "loop"]
print(words[0])

Common disgrace

Thinking the first item is at index 1. In Python, the first item is at index 0.

Trial by code

Make a list of three strings. Print the last item using a negative index.

What this creature is

An if statement runs a block of code only when a condition is true. You can add elif for other tests and else for a default.

Why you will regret ignoring it

Programs need to choose what to do. if lets you branch based on values, user input, or errors.

Example

score = 80
if score >= 50:
    print("Pass")
else:
    print("Review")

Common disgrace

Forgetting the colon (:) after if / elif / else, or not indenting the block under the condition — both cause syntax errors.

Trial by code

Write an if/else that prints one message if a number is greater than 0 and another if it is not.

What this creature is

A loop repeats code. A for loop goes through each item in a sequence. A while loop runs while a condition stays true.

Why you will regret ignoring it

Loops save you from copying the same code many times and let you process lists, files, or ranges efficiently.

Example

for word in ["a", "b", "c"]:
    print(word)

Common disgrace

Writing a while loop whose condition never becomes false, so the program runs forever until you stop it.

Trial by code

Use a for loop to print the numbers 1 through 5 (hint: range can help).

What this creature is

A function is a named block of code you define once and call by name. It can take parameters and return a value with return.

Why you will regret ignoring it

Functions organize logic, avoid repetition, and make programs easier to test and fix.

Example

def greet(name):
    return "Hello, " + name
print(greet("visitor"))

Common disgrace

Calling a function before Python has read its def, or using print when you meant to return a value to use later.

Trial by code

Define a function that doubles a number and returns it. Call it with 21 and print the result.

What this creature is

input() reads one line of text from the user (usually the terminal) and returns it as a string.

Why you will regret ignoring it

It lets programs respond to what the user types, which is essential for simple interactive programs.

Example

name = input("Your name: ")
print("Welcome,", name)

Common disgrace

Treating input as a number without converting — input always returns a string until you convert with int(), float(), etc.

Trial by code

Ask for two words using input() and print them on one line with a space between them.

What this creature is

print() writes values to standard output (usually the terminal) as text. It adds a newline at the end unless you change end.

Why you will regret ignoring it

Printing is the simplest way to see what your program is doing while you learn and debug.

Example

print("Done.")
print(42, "items", sep=" | ")

Common disgrace

Printing inside a tight loop and producing so much output that you cannot find the line you care about.

Trial by code

Print three values on one line using print with sep and end set to values you choose.