New submission from 尤立宇:
PEP 498 says: (https://www.python.org/dev/peps/pep-0498/#escape-sequences)
Scanning an f-string for expressions happens after escape sequences are
decoded. Because hex(ord('{')) == 0x7b , the f-string f'\u007b4*10}' is decoded
to f'{4*10}' , which evaluates as the integer 40:
>>> f'\u007b4*10}'
'40'
However, in python3.6.0b3, the '{' from '\u007b4' does not start an expression,
making the remaining '}' invalid:
>>> f'\u007b4*10}'
File "<stdin>", line 1
SyntaxError: f-string: single '}' is not allowed
There's even a test case for it: (Lib/test/test_fstring.py:383)
def test_no_escapes_for_braces(self):
# \x7b is '{'. Make sure it doesn't start an expression.
self.assertEqual(f'\x7b2}}', '{2}')
self.assertEqual(f'\x7b2', '{2')
self.assertEqual(f'\u007b2', '{2')
self.assertEqual(f'\N{LEFT CURLY BRACKET}2\N{RIGHT CURLY BRACKET}',
'{2}')
----------
components: Interpreter Core
messages: 279927
nosy: 尤立宇
priority: normal
severity: normal
status: open
title: fstring's '{' from escape sequences does not start an expression
type: behavior
versions: Python 3.6
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue28590>
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