[issue32954] Lazy Literal String Interpolation (PEP-498-based fl-strings)
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[issue29715] Argparse improperly handles "-_"
Changes by Mateusz Bysiek <r...@mbdev.pl>: -- title: Arparse improperly handles "-_" -> Argparse improperly handles "-_" ___ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue29715> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue28964] AST literal_eval exceptions provide no information about line number
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[issue10399] AST Optimization: inlining of function calls
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[issue11549] Build-out an AST optimizer, moving some functionality out of the peephole optimizer
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[issue29471] AST: add an attribute to FunctionDef to distinguish functions from generators and coroutines
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[issue24119] Carry comments with the AST
Mateusz Bysiek added the comment: For some time now, there's an alternate ast implementation https://github.com/python/typed_ast that carries PEP 484 type comments with the AST as attributes of certain nodes. Their approach is described here: https://github.com/python/typed_ast/blob/master/typed_ast/ast3.py#L5 If type comments become mainstream in Python, could this approach maybe be adopted as official Python AST at some point? -- nosy: +mbdevpl ___ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue24119> ___ ___ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue29051] Improve error reporting involving f-strings (PEP 498)
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[issue29814] parsing f-strings -- opening brace of expression gets duplicated when preceeded by backslash
New submission from Mateusz Bysiek:
with Python 3.6.0 and the following script:
```
#!/usr/bin/env python3.6
import ast
code1 = '''"\\{x}"'''
code2 = '''f"\\{x}"'''
tree1 = ast.parse(code1, mode='eval')
print(ast.dump(tree1))
tree2 = ast.parse(code2, mode='eval')
print(ast.dump(tree2))
```
I get the following output:
```
Expression(body=Str(s='\\{x}'))
Expression(body=JoinedStr(values=[Str(s='\\{'),
FormattedValue(value=Name(id='x', ctx=Load()), conversion=-1,
format_spec=None)]))
```
Therefore, the normal string is `'\\{x}'`.
But the f-string has two parts: `'\\{'` and an expression `Name(id='x',
ctx=Load())`.
Where does the `{` in the string part of f-string come from? I can't believe
this is the intended behavior... Or, is it?
When I escape the backslash once like above, what gets parsed is actually
unescaped backslash. So this might just boil down to inconsistency in parsing
`\{` in normal vs. f-strings.
I originally discovered this in typed_ast
https://github.com/python/typed_ast/issues/34 but the behaviour of ast is
identical and since developers of typed_ast aim at compatibility with ast, I
bring this issue here.
--
components: Library (Lib)
messages: 289642
nosy: mbdevpl
priority: normal
severity: normal
status: open
title: parsing f-strings -- opening brace of expression gets duplicated when
preceeded by backslash
type: behavior
versions: Python 3.6
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