python · serhiy-storchaka · Mar 6, 2025 · Mar 5, 2025 · Mar 6, 2025 · Mar 6, 2025
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
@@ -768,6 +768,8 @@ def test_format(self):
        self.assertEqual(format(x, '<21._f'), '123456.123_456       ')
        self.assertEqual(format(x, '+.11_e'), '+1.234_561_234_56e+05')
        self.assertEqual(format(x, '+.11,e'), '+1.234,561,234,56e+05')
+        self.assertEqual(format(x, '019_._f'), '000_123_456.123_456')
+        self.assertEqual(format(x, '021_.10_f'), '123_456.123_456_000_0')

        self.assertRaises(ValueError, format, x, '._6f')
        self.assertRaises(ValueError, format, x, '.,_f')

diff --git a/Python/formatter_unicode.c b/Python/formatter_unicode.c
@@ -578,14 +578,31 @@ calc_number_widths(NumberFieldWidths *spec, Py_ssize_t n_prefix,
        }
    }

+    if (spec->n_frac == 0) {
+        spec->n_grouped_frac_digits = 0;
+    }
+    else {
+        Py_UCS4 grouping_maxchar;
+        spec->n_grouped_frac_digits = _PyUnicode_InsertThousandsGrouping(
+            NULL, 0,
+            NULL, 0, spec->n_frac,
+            spec->n_frac,
+            locale->grouping, locale->frac_thousands_sep, &grouping_maxchar, 1);
+        if (spec->n_grouped_frac_digits == -1) {
+            return -1;
+        }
+        *maxchar = Py_MAX(*maxchar, grouping_maxchar);
+    }
+
    /* The number of chars used for non-digits and non-padding. */
    n_non_digit_non_padding = spec->n_sign + spec->n_prefix + spec->n_decimal +
        + spec->n_frac + spec->n_remainder;

    /* min_width can go negative, that's okay. format->width == -1 means
       we don't care. */
    if (format->fill_char == '0' && format->align == '=')
-        spec->n_min_width = format->width - n_non_digit_non_padding;
+        spec->n_min_width = (format->width - n_non_digit_non_padding
+                             + spec->n_frac - spec->n_grouped_frac_digits);
    else
        spec->n_min_width = 0;

@@ -607,22 +624,6 @@ calc_number_widths(NumberFieldWidths *spec, Py_ssize_t n_prefix,
        *maxchar = Py_MAX(*maxchar, grouping_maxchar);
    }

-    if (spec->n_frac == 0) {
-        spec->n_grouped_frac_digits = 0;
-    }
-    else {
-        Py_UCS4 grouping_maxchar;
-        spec->n_grouped_frac_digits = _PyUnicode_InsertThousandsGrouping(
-            NULL, 0,
-            NULL, 0, spec->n_frac,
-            spec->n_frac,
-            locale->grouping, locale->frac_thousands_sep, &grouping_maxchar, 1);
-        if (spec->n_grouped_frac_digits == -1) {
-            return -1;
-        }
-        *maxchar = Py_MAX(*maxchar, grouping_maxchar);
-    }
-
    /* Given the desired width and the total of digit and non-digit
       space we consume, see if we need any padding. format->width can
       be negative (meaning no padding), but this code still works in