The Python Tutorial¶
Python is an easy to learn, powerful programming language. It has efficient high-level data structures and a simple but effective approach to object-oriented programming. Python’s elegant syntax and dynamic typing, together with its interpreted nature, make it an ideal language for scripting and rapid application development in many areas on most platforms.
The Python interpreter and the extensive standard library are freely available in source or binary form for all major platforms from the Python web site, https://www.python.org/, and may be freely distributed. The same site also contains distributions of and pointers to many free third party Python modules, programs and tools, and additional documentation.
The Python interpreter is easily extended with new functions and data types implemented in C or C++ (or other languages callable from C). Python is also suitable as an extension language for customizable applications.
This tutorial introduces the reader informally to the basic concepts and features of the Python language and system. It helps to have a Python interpreter handy for hands-on experience, but all examples are self-contained, so the tutorial can be read off-line as well.
For a description of standard objects and modules, see The Python Standard Library . The Python Language Reference gives a more formal definition of the language. To write extensions in C or C++, read Extending and Embedding the Python Interpreter and Python/C API Reference Manual . There are also several books covering Python in depth.
This tutorial does not attempt to be comprehensive and cover every single feature, or even every commonly used feature. Instead, it introduces many of Python’s most noteworthy features, and will give you a good idea of the language’s flavor and style. After reading it, you will be able to read and write Python modules and programs, and you will be ready to learn more about the various Python library modules described in The Python Standard Library .
The Glossary is also worth going through.
- 1. Whetting Your Appetite
- 2. Using the Python Interpreter
- 2.1. Invoking the Interpreter
- 2.1.1. Argument Passing
- 2.1.2. Interactive Mode
- 2.2.1. Source Code Encoding
- 3.1. Using Python as a Calculator
- 3.1.1. Numbers
- 3.1.2. Strings
- 3.1.3. Lists
- 4.1. if Statements
- 4.2. for Statements
- 4.3. The range() Function
- 4.4. break and continue Statements, and else Clauses on Loops
- 4.5. pass Statements
- 4.6. match Statements
- 4.7. Defining Functions
- 4.8. More on Defining Functions
- 4.8.1. Default Argument Values
- 4.8.2. Keyword Arguments
- 4.8.3. Special parameters
- 4.8.3.1. Positional-or-Keyword Arguments
- 4.8.3.2. Positional-Only Parameters
- 4.8.3.3. Keyword-Only Arguments
- 4.8.3.4. Function Examples
- 4.8.3.5. Recap
- 5.1. More on Lists
- 5.1.1. Using Lists as Stacks
- 5.1.2. Using Lists as Queues
- 5.1.3. List Comprehensions
- 5.1.4. Nested List Comprehensions
- 6.1. More on Modules
- 6.1.1. Executing modules as scripts
- 6.1.2. The Module Search Path
- 6.1.3. “Compiled” Python files
- 6.4.1. Importing * From a Package
- 6.4.2. Intra-package References
- 6.4.3. Packages in Multiple Directories
- 7.1. Fancier Output Formatting
- 7.1.1. Formatted String Literals
- 7.1.2. The String format() Method
- 7.1.3. Manual String Formatting
- 7.1.4. Old string formatting
- 7.2.1. Methods of File Objects
- 7.2.2. Saving structured data with json
- 8.1. Syntax Errors
- 8.2. Exceptions
- 8.3. Handling Exceptions
- 8.4. Raising Exceptions
- 8.5. Exception Chaining
- 8.6. User-defined Exceptions
- 8.7. Defining Clean-up Actions
- 8.8. Predefined Clean-up Actions
- 8.9. Raising and Handling Multiple Unrelated Exceptions
- 8.10. Enriching Exceptions with Notes
- 9.1. A Word About Names and Objects
- 9.2. Python Scopes and Namespaces
- 9.2.1. Scopes and Namespaces Example
- 9.3.1. Class Definition Syntax
- 9.3.2. Class Objects
- 9.3.3. Instance Objects
- 9.3.4. Method Objects
- 9.3.5. Class and Instance Variables
- 9.5.1. Multiple Inheritance
- 10.1. Operating System Interface
- 10.2. File Wildcards
- 10.3. Command Line Arguments
- 10.4. Error Output Redirection and Program Termination
- 10.5. String Pattern Matching
- 10.6. Mathematics
- 10.7. Internet Access
- 10.8. Dates and Times
- 10.9. Data Compression
- 10.10. Performance Measurement
- 10.11. Quality Control
- 10.12. Batteries Included
- 11.1. Output Formatting
- 11.2. Templating
- 11.3. Working with Binary Data Record Layouts
- 11.4. Multi-threading
- 11.5. Logging
- 11.6. Weak References
- 11.7. Tools for Working with Lists
- 11.8. Decimal Floating Point Arithmetic
- 12.1. Introduction
- 12.2. Creating Virtual Environments
- 12.3. Managing Packages with pip
- 14.1. Tab Completion and History Editing
- 14.2. Alternatives to the Interactive Interpreter
- 15.1. Representation Error
- 16.1. Interactive Mode
- 16.1.1. Error Handling
- 16.1.2. Executable Python Scripts
- 16.1.3. The Interactive Startup File
- 16.1.4. The Customization Modules
Creating Python Programs
After reading the Python tutorial so far, you should have a basic understanding of Python and the REPL. Even though the latter can be very useful, you probably noticed in the last example that the REPL has its limits. It’s nice for quick experiments, but:
- It’s really hard to enter more than a few lines
- It’s hard to go back to previous lines
- There’s no syntax highlighting
- We can’t store our programs and re-use them later on
If we want to store our programs and use a decent editor, we need to simply:
No worries, we’ll go over it step by step.
1. Create a Python file
We need to create a so-called plain text file, meaning there’s nothing special about this file. It’s just text. Sounds simple, but it’s not. For example, if you start Word or a similar program, enter some text, and save it, you don’t end up with plain text.
Text processing software like Word will add all kinds of extra codes to define the markup, allow for images to be included, etcetera. It looks a little like HTML, in fact, which is used to create websites (see this HTML tutorial for an introduction).
So what should we use?
If you’re on Windows, try Notepad. It’s a plain text editor that does not add any markup. It’s a horrible way to create Python programs, but we’ll explore better options later on.
If you’re on Linux, you could open a terminal and try a text editor like nano or vim (the last one is hard to use if you haven’t read the manual, though). Many Linux installations include a GUI text editor too, like gedit.
MacOS comes with a program called TextEdit.
2. Enter the code
Now it’s time to enter some code. We’ll keep it super simple for now. Just enter something like:
On Windows, it should look like this:
3. Save the file
Save the file. The most important thing to look out for is the file extension. Python files end with the .py extension. Call your file helloworld.py . In Notepad, you need to click the dropdown list called ‘Save as type’ and select All files (*.* ):
4. Execute a Python program file
Now that you saved the file, we can execute it. There are two options, and most often you want to go for option one:
- Open a terminal or command prompt, go to the file’s directory, and execute it with the python3 command
- Find the file with Windows explorer, right click, open with ‘Python 3.X’.
If you try option two, you’ll find out that the program flashes on the screen shortly, and you won’t see the output because the window closes itself directly after the text is printed to the screen. So now you know why you want option one! If you create more advanced programs that keep running instead of quitting directly, option two can be an OK way to start a Python script.
Note: I’ll demonstrate using Windows, but this works the same on Linux and MacOS. Instead of opening a Command Prompt or Windows Terminal, you open a MacOS terminal or Linux terminal.
- Open the start menu and type ‘Command Prompt.’ It might be named differently if your OS is configured with another language than English. Hint: Create a new profile with English settings. It may be helpful because most examples on the web and in books assume English settings.
- cd to the directory where you stored your file. In my case, it’s C:\python.land
- Run the program with the command python3 helloworld.py
The output should look like this:
Congrats, You did it. You wrote a Python program, saved it to a file, and executed it like a boss! Don’t celebrate too hard, though. You don’t want to develop Python software using Notepad or other simple text editors. What you really want is a Python IDE: an Integrated Development Environment. Sounds scary, but it’s not!
Get certified with our courses
Our premium courses offer a superior user experience with small, easy-to-digest lessons, progress tracking, quizzes to test your knowledge, and practice sessions. Each course will earn you a downloadable course certificate.
Learn more
This article is part of my Python tutorial. You can head over to the start of the tutorial here. You can navigate this tutorial using the buttons at the top and bottom of the articles. To get an overview of all articles in the tutorial, please use the fold-out menu at the top.
If you liked this article, you might also like to read the following articles:
Leave a Comment Cancel reply
You must be logged in to post a comment.
You are browsing the free Python tutorial. Make sure to check out my full Python courses as well.
Subscribe to my newsletter for Python news, tips, and tricks!
- 2.1. Invoking the Interpreter
