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bpo-27772: Make preciding width with 0 valid in string format. #11270

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serhiy-storchaka merged 4 commits into from
Jan 25, 2021
Merged

bpo-27772: Make preciding width with 0 valid in string format. #11270

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bpo-27772: Make preciding width with 0 valid in string format.
serhiy-storchaka Dec 20, 2018
d1d048e
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serhiy-storchaka Jan 24, 2021
49695d1
Merge branch 'master' into format-str-default-align
serhiy-storchaka Jan 24, 2021
423906d
Merge branch 'format-str-default-align' of github.com:serhiy-storchak…
serhiy-storchaka Jan 24, 2021
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8 changes: 6 additions & 2 deletions Doc/library/string.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -347,8 +347,8 @@ The meaning of the various alignment options is as follows:
| ``'='`` | Forces the padding to be placed after the sign (if any) |
| | but before the digits. This is used for printing fields |
| | in the form '+000000120'. This alignment option is only |
| | valid for numeric types. It becomes the default when '0'|
| | immediately precedes the field width. |
| | valid for numeric types. It becomes the default for |
| | numbers when '0' immediately precedes the field width. |
+---------+----------------------------------------------------------+
| ``'^'`` | Forces the field to be centered within the available |
| | space. |
Expand Down Expand Up @@ -424,6 +424,10 @@ When no explicit alignment is given, preceding the *width* field by a zero
sign-aware zero-padding for numeric types. This is equivalent to a *fill*
character of ``'0'`` with an *alignment* type of ``'='``.

.. versionchanged:: 3.10
Preceding the *width* field by ``'0'`` no longer affects the default
alignment for strings.

The *precision* is a decimal number indicating how many digits should be
displayed after the decimal point for a floating point value formatted with
``'f'`` and ``'F'``, or before and after the decimal point for a floating point
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6 changes: 6 additions & 0 deletions Lib/test/test_unicode.py
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Expand Up @@ -1098,6 +1098,12 @@ def __repr__(self):
self.assertEqual('{0:^8s}'.format('result'), ' result ')
self.assertEqual('{0:^9s}'.format('result'), ' result ')
self.assertEqual('{0:^10s}'.format('result'), ' result ')
self.assertEqual('{0:8s}'.format('result'), 'result ')
self.assertEqual('{0:0s}'.format('result'), 'result')
self.assertEqual('{0:08s}'.format('result'), 'result00')
self.assertEqual('{0:<08s}'.format('result'), 'result00')
self.assertEqual('{0:>08s}'.format('result'), '00result')
self.assertEqual('{0:^08s}'.format('result'), '0result0')
self.assertEqual('{0:10000}'.format('a'), 'a' + ' ' * 9999)
self.assertEqual('{0:10000}'.format(''), ' ' * 10000)
self.assertEqual('{0:10000000}'.format(''), ' ' * 10000000)
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2018-12-20-23-59-23.bpo-27772.idHEcj.rst
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@@ -0,0 +1,2 @@
In string formatting, preceding the *width* field by ``'0'`` no longer
affects the default alignment for strings.
2 changes: 1 addition & 1 deletion Python/formatter_unicode.c
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Expand Up @@ -219,7 +219,7 @@ parse_internal_render_format_spec(PyObject *format_spec,
/* The special case for 0-padding (backwards compat) */
if (!fill_char_specified && end-pos >= 1 && READ_spec(pos) == '0') {
format->fill_char = '0';
if (!align_specified) {
if (!align_specified && default_align == '>') {
format->align = '=';
}
++pos;
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