Python Introduction

Python is a general-purpose programming language known for code that is short and easy to read. This lesson explains what Python is, why it is so popular, and what happens when you run a Python program.

What is Python?

Python is a high-level, interpreted, general-purpose programming language.

• High-level means you work with ideas such as lists, text and files, not with memory addresses.
• Interpreted means you run the source file directly with the python command. There is no separate compile step to manage.
• General-purpose means it is not tied to one job. The same language builds web servers, test frameworks and data reports.

Here is a complete Python program. It stores some test results and prints a summary:

results = {"login": "pass", "search": "pass", "checkout": "fail"} passed = [name for name, status in results.items() if status == "pass"]print("Tests run:", len(results))print("Passed:", ", ".join(passed))

Tests run: 3
Passed: login, search

You do not need to understand every line yet. Notice how little punctuation there is: no semicolons, no curly braces around blocks, no type declarations.

A short history

The name comes from the comedy group Monty Python, not from the snake.

Key features of Python

Dynamic typing in action: the same name can hold values of different types, and type() tells you what it holds right now.

value = 42print(type(value)) value = "forty-two"print(type(value))

<class 'int'>
<class 'str'>

The Zen of Python

Python’s design ideas are written down as a short poem. Run import this to print it:

import this

The Zen of Python, by Tim Peters

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

What is Python used for?

• Test automation: pytest, Selenium, Playwright and requests for UI and API testing.
• Web development: Django, Flask and FastAPI power web sites and REST APIs.
• Data analysis: NumPy, Pandas and Matplotlib turn raw data into answers.
• Machine learning and AI: scikit-learn, PyTorch and TensorFlow.
• Scripting and automation: renaming files, sending reports, cleaning spreadsheets.
• DevOps and cloud tooling: Ansible, AWS and Azure SDKs, CI scripts.

How Python runs your code

When you run python hello.py:

1. The interpreter reads your source code and checks the syntax.
2. It compiles the code to bytecode, a simple instruction format.
3. The Python virtual machine executes the bytecode line by line.

You can see which interpreter is running and where with the sys module:

import sys, platform print(platform.python_implementation())print(sys.version_info.major, sys.version_info.minor)

CPython
3 15

Check your understanding

Program Practice

Ready to write code? The basic programs use only variables, arithmetic and print(), so they are a good first set.

Python introduction FAQ