René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Remove `TODO` comment in `_pydatetime._isoweek1monday`","articleBody":"# Feature or enhancement\n\n### Proposal:\n\nAccording to the existing note `# XXX This could be done more efficiently`, the `_isoweek1monday` function can be improved.\n\n### Current Implementation:\n\n```python\ndef _isoweek1monday(year):\n    # Helper to calculate the day number of the Monday starting week 1\n    # XXX This could be done more efficiently\n    THURSDAY = 3\n    firstday = _ymd2ord(year, 1, 1)\n    firstweekday = (firstday + 6) % 7  # See weekday() above\n    week1monday = firstday - firstweekday\n    if firstweekday \u003e THURSDAY:\n        week1monday += 7\n    return week1monday\n```\n\n### Proposed Change\nReplace the current implementation with a simplified logic that is both more performant and easier to understand.\n```python\ndef _isoweek1monday_new(year):\n    # Calculate the ordinal day of the Monday starting ISO week 1.\n    # ISO week 1 is defined as the week that contains January 4th.\n    jan4 = _ymd2ord(year, 1, 4)\n    jan4_weekday = (jan4 + 6) % 7\n    return jan4 - jan4_weekday\n```\n\n### Rationale\n\nThe new logic:\n\t1.\tAligns directly with the ISO week definition, which makes it easier to comprehend.\n\t2.\tReduces unnecessary computations, improving performance slightly.\n\n\n### Validation and Performance Comparison\nUsing timeit to compare the current and proposed implementations:\n```python\nimport timeit\nfrom _pydatetime import _isoweek1monday, _ymd2ord\n\ndef _isoweek1monday_new(year):\n    jan4 = _ymd2ord(year, 1, 4)\n    jan4_weekday = (jan4 + 6) % 7\n    return jan4 - jan4_weekday\n\n# Validation results:\n# \u003e\u003e\u003e all(_isoweek1monday_new(i) == _isoweek1monday(i) for i in range(2000))\n# True\n\n# Timing results:\n# \u003e\u003e\u003e timeit.timeit('_isoweek1monday(2000)', globals=globals())\n# 0.4805744589539245\n# \u003e\u003e\u003e timeit.timeit('_isoweek1monday_new(2000)', globals=globals())\n# 0.4299807079951279\n```\n\n### Has this already been discussed elsewhere?\n\nNo response given\n\n### Links to previous discussion of this feature:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-127564\n* gh-128500\n* gh-128501\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/bombs-kim","@type":"Person","name":"bombs-kim"},"datePublished":"2024-12-03T11:30:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":11},"url":"https://github.com/127553/cpython/issues/127553"}