[New-bugs-announce] [issue10021] Format parser is too permissive

[Alexander Belopolsky]

New submission from Alexander Belopolsky <belopolsky at users.sourceforge.net>:

According to the Format String Syntax section [1], attribute_name must be an identifier.  However, the parser does not catch a violation of this rule and happily passes non-indentifier strings to getattribute:

>>> class X:
...    def __getattribute__(self, a): return 'foo'
... 
>>> '{.$#@}'.format(X())
'foo'
 
If this is a desirable feature, I think it should be clearly documented because in some cases, for example when formatted objects are proxies to  database entries, passing arbitrary strings to __getattribute__ may be wasteful at best and a security hole at worst.


[1] http://docs.python.org/dev/py3k/library/string.html#format-string-syntax

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components: Interpreter Core
messages: 117961
nosy: belopolsky
priority: normal
severity: normal
status: open
title: Format parser is too permissive
type: behavior
versions: Python 3.2

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue10021>
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