Skip to content

gh-124294: str.format() raises misleading error when using negative indices #124372

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 7 commits into from
Closed

gh-124294: str.format() raises misleading error when using negative indices #124372

Show file tree
Hide file tree
Changes from 5 commits
Commits
Show all changes
7 commits
Select commit Hold shift + click to select a range
2f24f22
Add error handling for invalid sequence index
makukha Sep 23, 2024
470fd35
Merge remote-tracking branch 'upstream/main' into str-format-negative
makukha Sep 23, 2024
201e4b1
Add tests
makukha Sep 24, 2024
0d67891
Add news entry
makukha Sep 24, 2024
7ec5eb8
Fix errors and update error message
makukha Sep 24, 2024
080802a
Updatee tests
makukha Sep 24, 2024
8eeca72
PEP7-ize
makukha Sep 24, 2024
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 4 additions & 0 deletions Lib/test/test_str.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1388,6 +1388,10 @@ def __repr__(self):
self.assertEqual("{!s}".format(n), 'N(data)')
self.assertRaises(TypeError, "{}".format, n)

# String index for sequences
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Maybe you could delete this comment since the user won't see it anyway.

self.assertRaises(TypeError, "{[s]}".format, "abc")
self.assertRaises(TypeError, "{[-1]}".format, "abc")
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

This is something, that already fails with TypeError in the main. I think you should test actual error messages with assertRaises's msg argument or using assertRaisesRegex().


def test_format_map(self):
self.assertEqual(''.format_map({}), '')
self.assertEqual('a'.format_map({}), 'a')
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2024-09-24-11-12-09.gh-issue-124294.jBPOm1.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
More informative error message in :func:`str.format` when passing negative
integer or string index to sequence.
14 changes: 13 additions & 1 deletion Objects/stringlib/unicode_format.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -462,8 +462,20 @@ get_field_object(SubString *input, PyObject *args, PyObject *kwargs,
tmp = getattr(obj, &name);
else
/* getitem lookup "[]" */
if (index == -1)
if (index == -1) {
if (PySequence_Check(obj)) {
/* string index can't be passed to sequence */
PyObject *str = SubString_new_object(&name);
if (str != NULL)
Copy link
Contributor

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Suggested change
if (str != NULL)
if (str)

Also beware PEP 7: "braces are required everywhere, even where C permits them to be omitted".

PyErr_Format(PyExc_TypeError,
"Index must be a sequence of digits, string %R "
"is not allowed",
str);
Py_XDECREF(str);
goto error;
}
tmp = getitem_str(obj, &name);
}
else
if (PySequence_Check(obj))
tmp = getitem_sequence(obj, index);
Expand Down
Loading