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gh-138005: Document that CSV skipinitialspace=True and delimiter=' ' require quotation for empty fields #138006

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gh-138005: Document that CSV skipinitialspace=True and delimiter=' ' require quotation for empty fields #138006

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@maurycy maurycy commented Aug 20, 2025 •
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Please see for the code:

  • cpython/Modules/_csv.c

    Lines 1253 to 1267 in 7dc42b6

    if (!field_len && dialect->delimiter == ' ' && dialect->skipinitialspace) {
    if (dialect->quoting == QUOTE_NONE ||
    (field == NULL &&
    (dialect->quoting == QUOTE_STRINGS ||
    dialect->quoting == QUOTE_NOTNULL)))
    {
    PyErr_Format(self->error_obj,
    "empty field must be quoted if delimiter is a space "
    "and skipinitialspace is true");
    return 0;
    }
    quoted = 1;
    }
    rec_len = join_append_data(self, field_kind, field_data, field_len,
    &quoted, 0);

Please see the test:

The behavior is intentional since gh-115721, so the only sensible route is to update the docs.

📚 Documentation preview 📚: https://cpython-previews--138006.org.readthedocs.build/

@bedevere-app bedevere-app bot added awaiting review docs Documentation in the Doc dir skip news labels Aug 20, 2025
@github-project-automation github-project-automation bot moved this to Todo in Docs PRs Aug 20, 2025
@bedevere-app bedevere-app bot mentioned this pull request Aug 20, 2025
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serhiy-storchaka
serhiy-storchaka reviewed Aug 21, 2025
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I think this is too verbose. The note takes up a lot of space and attracts a disproportionate amount of attention. Most users will never encounter this, and if they do, this behavior is expected and therefore does not require any special explanation.

Could you please limit yourself to one short sentence? That such CSV files cannot contain empty fields.

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maurycy commented Aug 21, 2025

I think this is too verbose. The note takes up a lot of space and attracts a disproportionate amount of attention. Most users will never encounter this, and if they do, this behavior is expected and therefore does not require any special explanation.

Could you please limit yourself to one short sentence? That such CSV files cannot contain empty fields.

Thank you for taking a look. Made it much shorter:

serhiy-storchaka
serhiy-storchaka approved these changes Aug 22, 2025
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LGTM. 👍

@serhiy-storchaka serhiy-storchaka added needs backport to 3.13 bugs and security fixes needs backport to 3.14 bugs and security fixes labels Aug 22, 2025
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