[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Roundup Robot]

Change by Roundup Robot :


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nosy: +python-dev
nosy_count: 3.0 -> 4.0
pull_requests: +20911
pull_request: https://github.com/python/cpython/pull/21767

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Maxwell Bernstein]

Maxwell Bernstein  added the comment:

Okay, well it doesn't provide the desired behavior of raising the error when 
switching back and forth between manual and auto numbering, so I am looking 
into that.

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Maxwell Bernstein]

Maxwell Bernstein  added the comment:

Looks like the patch solves my problem, so I am going to update my PR sometime 
today.

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Maxwell Bernstein]

Maxwell Bernstein  added the comment:

I'll take a look at the patch and see if this solves my problem. If it does, 
I'll update my PR with tests.

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Eric V. Smith]

Eric V. Smith  added the comment:

It would be good if someone could convert this to a pull request and beef up 
the tests.

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Eric V. Smith]

Change by Eric V. Smith :


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nosy: +tekknolagi

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Eric V. Smith]

Change by Eric V. Smith :


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versions: +Python 3.7, Python 3.8, Python 3.9 -Python 3.5, Python 3.6

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Ned Deily]

Changes by Ned Deily :


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nosy: +eric.smith
stage:  -> patch review
versions:  -Python 2.7, Python 3.2, Python 3.3, Python 3.4

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Tommy Beadle]

Changes by Tommy Beadle :


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keywords: +patch
Added file: 
http://bugs.python.org/file43376/0001-Issue-27307-Support-index-attribute-access-for-unnum.patch

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[issue27307] string.Formatter does not support key/attribute access on unnumbered fields

[Tommy Beadle]

New submission from Tommy Beadle:

Support for unnumbered fields in string.Formatter.format was added in 
http://bugs.python.org/issue13598, however, it does not support accessing an 
index or attribute of an unnumbered field like str.format does.  Instead, it 
raises an unhelpful "KeyError: ''":

In [1]: import string

In [2]: fmt = string.Formatter()

In [3]: fmt.format('{[0]}', ['a', 'b'])
---
KeyError  Traceback (most recent call last)
 in ()
> 1 fmt.format('{[0]}', ['a', 'b'])

/usr/lib64/python2.7/string.pyc in format(*args, **kwargs)
557 raise TypeError("format() missing 1 required positional 
"
558 "argument: 'format_string'")
--> 559 return self.vformat(format_string, args, kwargs)
560 
561 def vformat(self, format_string, args, kwargs):

/usr/lib64/python2.7/string.pyc in vformat(self, format_string, args, kwargs)
561 def vformat(self, format_string, args, kwargs):
562 used_args = set()
--> 563 result = self._vformat(format_string, args, kwargs, used_args, 
2)
564 self.check_unused_args(used_args, args, kwargs)
565 return result

/usr/lib64/python2.7/string.pyc in _vformat(self, format_string, args, kwargs, 
used_args, recursion_depth)
583 # given the field_name, find the object it references
584 #  and the argument it came from
--> 585 obj, arg_used = self.get_field(field_name, args, kwargs)
586 used_args.add(arg_used)
587 

/usr/lib64/python2.7/string.pyc in get_field(self, field_name, args, kwargs)
644 first, rest = field_name._formatter_field_name_split()
645 
--> 646 obj = self.get_value(first, args, kwargs)
647 
648 # loop through the rest of the field_name, doing

/usr/lib64/python2.7/string.pyc in get_value(self, key, args, kwargs)
603 return args[key]
604 else:
--> 605 return kwargs[key]
606 
607 

KeyError: ''


The attached patch adds this functionality.

aronancher asked in http://bugs.python.org/issue13598#msg218114 if the original 
patch was going to make it in to python 2.7.  Perhaps that could get a look?

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components: Library (Lib)
messages: 268452
nosy: tbeadle
priority: normal
severity: normal
status: open
title: string.Formatter does not support key/attribute access on unnumbered 
fields
type: behavior
versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6

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