Category: Python
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Python version at runtime: sys.version vs sys.version_info
Find the version of Python: To use it in a program, you want version_info:
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Python Enum auto(): Generating unique values automatically
Want a Python Enum, but don’t care about the values? Use auto: You can now use Days.SUN and Days.MON. With auto, you care the Enum’s values are different, not what they are.
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Python Enum iteration: Looping over __members__.items()
Want to iterate over a Python Enum? __members__ returns a dict-like object, and it supports items(): SUN: 1MON: 2TUE: 3[etc]
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Python Enum duplicate values: Preventing aliases with @unique
Normally, Python doesn’t enforce uniqueness on Enum values: The @unique decorator enforces:
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Python Enum sorting: Use IntEnum for comparable members
Want your Python Enum class to be sortable? The regular Enum doesn’t do it, but IntEnum does: Days.SUN < Days.THU # True!Days.MON > Days.WED # False!
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Python enums: Symbolic constants that print nicely but don’t sort
Enums are a great addition to Python: They print nicer and are symbolic! But… not sortable (yet).
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Python constants: Blocking reassignment with Final and mypy
Can you get Python to enforce constants? Yes, with type checking: Ruff won’t complain. Instead, type it as Final and run mypy: mypy myprog.pymyprog.py:6: error: Cannot assign to final name “NAME” [misc]
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Immutable vs. constant in Python: Why constants aren’t enforced
About immutable vs. constant in Python: – Immutable: The value cannot change. If you own an immutable shirt, you can’t change its color, or add/remove a button.– Constant: Once assigned, a name will always refer to a value. But: Python’s constants are unenforced conventions!
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Python dict.items(): Set operations on key-value pairs
Want the unique key-value pairs from two Python dicts? dict.items() returns a set-like object: This returns the unique key-value pairs: {(‘b’, 20), (‘a’, 10), (‘d’, 40), (‘c’, 30)}
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Python dict.keys(): Using set operators on dictionary keys
Want the unique keys from two Python dicts? dict.keys() returns a set-like object, supporting set operators: