Python or Python3. What is the difference?

Python vs. Python3: Understanding the Key Differences

Explore the historical context, syntax changes, and practical implications of Python 2 versus Python 3, and why Python 3 is the standard today.

For newcomers to the Python ecosystem, the terms "Python" and "Python3" can sometimes be a source of confusion. While both refer to the same programming language, "Python" often implicitly refers to the latest stable version (which is Python 3.x), whereas "Python2" (or just "Python" in older contexts) refers to the now-deprecated Python 2.x series. This article aims to clarify the distinctions, highlight the most significant changes, and explain why Python 3 is the undisputed standard for modern development.

A Brief History: The Split and Evolution

Python 2.0 was released in 2000, and Python 3.0 (also known as "Python 3000" or "Py3k") followed in 2008. The key difference was that Python 3.0 was designed to be backward-incompatible, meaning code written for Python 2 would not necessarily run on Python 3 without modifications. This decision was made to clean up inconsistencies, remove old ways of doing things, and introduce significant improvements that were difficult to implement while maintaining backward compatibility.

The transition period was lengthy, with Python 2.7 being the last major release in the 2.x series, maintained until its End-of-Life (EOL) on January 1, 2020. Since then, Python 2 no longer receives official support, security updates, or bug fixes, making its use in production environments highly discouraged.

flowchart TD
    A[Python 2.0 Released (2000)] --> B[Python 2.x Development]
    B --> C{Backward Compatibility?}
    C -- No --> D[Python 3.0 Released (2008)]
    D --> E[Python 3.x Development]
    B --> F[Python 2.7 Last Major Release (2010)]
    F --> G[Python 2.7 End-of-Life (2020)]
    G -- No further support --> H[Modern Python Development (Python 3.x)]
    E --> H

Timeline of Python 2 and Python 3 Evolution

Key Syntactic and Semantic Differences

The changes between Python 2 and Python 3 are extensive, touching upon fundamental aspects of the language. Understanding these differences is crucial for anyone encountering older Python 2 code or migrating projects.

Print Statement vs. Print Function

One of the most visible changes is how output is handled. In Python 2, print was a statement; in Python 3, it's a function, requiring parentheses.

Integer Division

Python 2 performed integer division by default when dividing two integers, truncating the result. Python 3 changed this to floating-point division, providing a more intuitive result.

Unicode and String Handling

Perhaps the most significant change relates to string types. Python 2 had two string types: str (byte strings) and unicode (Unicode strings). Python 3 unified this, making str always Unicode and introducing bytes for raw byte sequences. This change addresses many internationalization and encoding issues.

Exceptions

Syntax for catching exceptions changed slightly, improving clarity and consistency.

Iterators and Views

Many functions that returned lists in Python 2 (like range(), map(), filter(), dictionary methods like keys(), values(), items()) now return iterators or view objects in Python 3. This is a memory optimization, especially beneficial for large datasets.

# Python 2
print "Hello, World!"
print 5 / 2

# Python 3
print("Hello, World!")
print(5 / 2)

Print statement vs. function and integer division

# Python 2
my_string = "Hello"
print type(my_string) # <type 'str'> (byte string)

# Python 3
my_string = "Hello"
print(type(my_string)) # <class 'str'> (Unicode string)
my_bytes = b"Hello"
print(type(my_bytes)) # <class 'bytes'>

String and bytes types in Python 2 vs. Python 3

Why Python 3 is the Standard

With Python 2 officially unsupported, Python 3 is the only viable choice for new development and the recommended target for migrating existing Python 2 applications. The benefits of Python 3 include:

• Active Development: All new features, performance improvements, and standard library updates are exclusively for Python 3.
• Security: Python 2 no longer receives security patches, leaving applications vulnerable.
• Modern Features: Python 3 includes numerous language enhancements, such as async/await for asynchronous programming, f-strings for easy string formatting, and improved type hinting.
• Community and Libraries: The vast majority of new and actively maintained third-party libraries are Python 3-only. Support for Python 2 in popular libraries has largely ceased.
• Future-Proofing: Developing in Python 3 ensures your projects are built on a modern, supported, and evolving platform.