Python Version Guides¶

import heapq

# Native max-heap functions (new!)
data = [3, 1, 4, 1, 5, 9]
heapq.heapify_max(data)        # O(n) - max-heap transform
heapq.heappush_max(data, 10)   # O(log n)
max_val = heapq.heappop_max(data)  # O(log n)

# Incremental GC: 10x better pause times for large heaps
# uuid4(): ~30% faster

# Experimental free-threading (no GIL)
# Build with: --disable-gil

# Experimental JIT compiler
# Enable with: PYTHON_JIT=1

# textwrap.indent(): 30% faster for large input

# Improved error messages
"test"[999]  # IndexError with better message

# Type parameter syntax (PEP 695)
def greet[T: str](x: T) -> T:
    return x

# Performance: 5-10% faster on average

# Exception groups and except* syntax
try:
    ...
except ExceptionGroup as eg:
    raise eg.derive(...)

# Inline caching for attributes
class Point:
    def __init__(self, x, y):
        self.x = x
        self.y = y

p = Point(1, 2)
# First access: cache miss
print(p.x)
# Repeated access: uses inline cache (much faster)

# 10-60% performance improvement overall

# Structural pattern matching
match value:
    case 1:
        print("one")
    case 2:
        print("two")
    case _:
        print("other")

# Type hints without import
def add(a: list[int], b: list[int]) -> list[int]:
    return [x + y for x, y in zip(a, b)]

# Dictionary operations
d1 = {'a': 1}
d2 = {'b': 2}
d3 = d1 | d2  # {'a': 1, 'b': 2}
d1 |= d2  # Update in place

# Walrus operator :=
if (n := len(a)) > 10:
    print(f"List too long ({n} elements)")

# Positional-only parameters
def func(x, /, y):
    # x is positional-only, y can be keyword
    pass

Python 3.8 → Python 3.9    Incremental improvements
Python 3.9 → Python 3.10   Minor improvements
Python 3.10 → Python 3.11  10-60% faster (significant!)
Python 3.11 → Python 3.12  5-10% faster
Python 3.12 → Python 3.13  Similar (experimental features)
Python 3.13 → Python 3.14  Better GC pauses, new heapq functions

# Test with newer version
uv python install 3.12
uv run --python 3.12 pytest  # Run tests

# Check for deprecations
uv run --python 3.12 python -W all your_script.py

# Pin version for this project
echo "3.11" > .python-version
uv sync  # Installs Python 3.11 and dependencies

# Use different version for one-off commands
uv run --python 3.12 python script.py