Glossary

A-Z reference of Python and programming terms used in this handbook.

A

Argument A value passed to a function when it is called. For example, in print("hello"), "hello" is an argument.

Attribute A value or method associated with an object. Accessed using dot notation: object.attribute. For example, "hello".upper is an attribute of the string.

B

Boolean A data type with two possible values: True or False. Used in conditional statements and logical operations.

Built-in A function, type, or constant that is part of Python and available without importing. Examples: print(), len(), int, True.

C

Class A blueprint for creating objects. Defines attributes and methods that instances of the class will have.

Collection A data structure that holds multiple items. Examples: list, tuple, set, dictionary.

Comprehension A concise way to create a collection by iterating over another collection and applying a condition or transformation. Examples: list comprehension, dictionary comprehension.

Conditional A statement that executes code based on whether a condition is true or false. Examples: if, elif, else.

D

Dictionary A collection of key-value pairs. Keys are unique and used to access values. Created with {} or dict().

Docstring A string that documents a function, class, or module. Written as the first statement using triple quotes: """...""".

E

Exception An error that occurs during program execution. Can be caught and handled with try/except blocks.

Expression A combination of values, variables, and operators that evaluates to a result. For example, 2 + 3 or x > 5.

F

File Path The location of a file on the filesystem. Can be absolute (from root) or relative (from current directory).

Function A reusable block of code that performs a specific task. Defined with def and called by name.

G

Generator A function that yields values one at a time instead of returning all at once. Created using yield keyword.

I

Immutable Cannot be changed after creation. Examples: strings, tuples, numbers. Opposite of mutable.

Import A statement that loads a module or specific items from a module into the current namespace. Examples: import os, from pathlib import Path.

Indentation Whitespace at the beginning of a line used to define code blocks in Python. Must be consistent (typically 4 spaces per level).

Index The position of an item in a sequence, starting from 0. For example, in [1, 2, 3], the index of 2 is 1.

Iterable An object that can be looped over. Examples: lists, tuples, strings, dictionaries, sets.

Iterator An object that produces values one at a time when iterated over. Created with iter() and advanced with next().

K

Key In a dictionary, the unique identifier used to access a value. For example, in {"name": "Alice"}, "name" is a key.

L

List A mutable collection of items in a specific order. Created with [] or list().

Loop A control structure that repeats a block of code. Examples: for loop, while loop.

M

Method A function associated with an object. Called using dot notation: object.method(). For example, "hello".upper().

Module A file containing Python code that can be imported and used in other programs. Typically has a .py extension.

Mutable Can be changed after creation. Examples: lists, dictionaries, sets. Opposite of immutable.

N

None A special value representing the absence of a value or null. Used as a default return value for functions that don't explicitly return.

O

Object An instance of a class. Everything in Python is an object, including numbers, strings, lists, and functions.

P

Package A directory containing Python modules and a special __init__.py file. Allows organizing related modules.

Parameter A variable in a function definition that receives a value when the function is called. For example, in def greet(name):, name is a parameter.

Path See "File Path".

pip The Python package installer. Used to install third-party packages from PyPI.

Project A collection of Python files and related resources organized for a specific purpose.

pytest A popular testing framework for Python. Used to write and run tests.

R

REPL Read-Eval-Print Loop. An interactive Python environment where you can type commands and see results immediately. Accessed by running python in the terminal.

Return Value The value that a function sends back to the caller. Specified with the return keyword.

S

Script A Python file designed to be run directly, typically containing a sequence of statements. Often has a if __name__ == "__main__": guard.

Set An unordered collection of unique items. Created with {} (with items) or set().

Slice A portion of a sequence extracted using the slice operator [start:stop:step]. For example, "hello"[1:4] returns "ell".

String A sequence of characters. Created with quotes: "hello" or 'hello'.

T

Tuple An immutable collection of items in a specific order. Created with () or tuple().

Type The category of a value, determining what operations can be performed on it. Examples: int, str, list, dict.

Type Hint An annotation indicating the expected type of a variable or function parameter. For example, def greet(name: str) -> str:.

V

Variable A named container that stores a value. Created by assignment: x = 10.

Virtual Environment An isolated Python environment on your system. Allows different projects to have different package versions without conflicts. Created with venv module.

W

While Loop A loop that repeats as long as a condition is true. Syntax: while condition: ....

Y

Yield A keyword used in generators to produce values one at a time. Similar to return but allows the function to resume later.