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GH-132661: Add string.templatelib.convert() #135217

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Merged
merged 4 commits into from
Jul 15, 2025
Merged

GH-132661: Add string.templatelib.convert() #135217

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d91d6fc
Add ``string.templatelib.convert()``
AA-Turner Jun 6, 2025
321164a
Remove documentation
AA-Turner Jul 15, 2025
9d59705
Avoid BytesWarning
AA-Turner Jul 15, 2025
125ce4e
Imperative mood
AA-Turner Jul 15, 2025
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17 changes: 12 additions & 5 deletions Lib/string/templatelib.py
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Original file line number Diff line number Diff line change
@@ -1,15 +1,22 @@
"""Support for template string literals (t-strings)."""

__all__ = [
"Interpolation",
"Template",
]

t = t"{0}"
Template = type(t)
Interpolation = type(t.interpolations[0])
del t

def convert(obj, /, conversion):
"""Convert *obj* using formatted string literal semantics."""
if conversion is None:
return obj
if conversion == 'r':
return repr(obj)
if conversion == 's':
return str(obj)
if conversion == 'a':
return ascii(obj)
raise ValueError(f'invalid conversion specifier: {conversion}')

def _template_unpickle(*args):
import itertools

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22 changes: 21 additions & 1 deletion Lib/test/test_string/test_templatelib.py
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
import pickle
import unittest
from collections.abc import Iterator, Iterable
from string.templatelib import Template, Interpolation
from string.templatelib import Template, Interpolation, convert

from test.test_string._support import TStringBaseCase, fstring

Expand Down Expand Up @@ -156,5 +156,25 @@ def test_exhausted(self):
self.assertRaises(StopIteration, next, template_iter)


class TestFunctions(unittest.TestCase):
def test_convert(self):
from fractions import Fraction

for obj in ('Café', None, 3.14, Fraction(1, 2)):
with self.subTest(f'{obj=}'):
self.assertEqual(convert(obj, None), obj)
self.assertEqual(convert(obj, 's'), str(obj))
self.assertEqual(convert(obj, 'r'), repr(obj))
self.assertEqual(convert(obj, 'a'), ascii(obj))

# Invalid conversion specifier
with self.assertRaises(ValueError):
convert(obj, 'z')
with self.assertRaises(ValueError):
convert(obj, 1)
with self.assertRaises(ValueError):
convert(obj, object())


if __name__ == '__main__':
unittest.main()
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