Python 2 vs Python 3

Python 3 is the present and future of the language. Python 2 reached End of Life (EOL) on January 1, 2020. However, understanding the differences is still important for maintaining legacy codebases and answering interview questions.

Major Differences

Print Statement vs Function

Python 2 uses print as a statement, while Python 3 makes it a function with more flexibility.

Integer Division

In Python 2, 3/2 returns 1 (floor division). In Python 3, 3/2 returns 1.5 (true division). Use // for explicit floor division in Python 3.

String Encoding

Python 2 strings are ASCII by default; you need a u"" prefix for Unicode. Python 3 strings are Unicode by default — a massive improvement for internationalization.

Other Key Differences

• range(): Py2 returns a list; Py3 returns a memory-efficient range object.
• dict methods: .keys(), .values(), .items() return views in Py3, not lists.
• Exceptions: except Exception, e: in Py2 becomes except Exception as e: in Py3.
• next(): iterator.next() in Py2 becomes next(iterator) in Py3.
• exec: Statement in Py2, function in Py3.
• Type annotations: Only available in Python 3.5+.
• f-strings: Only available in Python 3.6+.
• Walrus operator (:=): Only available in Python 3.8+.

Python 3.x Version Highlights

• 3.6: f-strings, type hints improvements, async/await
• 3.7: Data classes, __init_subclass__, dict ordering guaranteed
• 3.8: Walrus operator (:=), positional-only parameters
• 3.9: Dict merge operators (|, |=), built-in generic types
• 3.10: Structural pattern matching (match/case), better error messages
• 3.11: 10-60% faster than 3.10, exception groups, tomllib
• 3.12: Per-interpreter GIL (experimental), f-string improvements, type statement