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Issue #13598: Add auto-numbering of replacement fields to string.Formatter.

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This commit is contained in:
Eric V. Smith 2014-04-14 16:43:50 -04:00
parent efeb9da4ae
commit 7ce90743a1
3 changed files with 42 additions and 2 deletions
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23
Lib/string.py
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@ -169,7 +169,8 @@ class Formatter:
self.check_unused_args(used_args, args, kwargs)
return result
def _vformat(self, format_string, args, kwargs, used_args, recursion_depth):
def _vformat(self, format_string, args, kwargs, used_args, recursion_depth,
auto_arg_index=0):
if recursion_depth < 0:
raise ValueError('Max string recursion exceeded')
result = []
@ -185,6 +186,23 @@ class Formatter:
# this is some markup, find the object and do
# the formatting
# handle arg indexing when empty field_names are given.
if field_name == '':
if auto_arg_index is False:
raise ValueError('cannot switch from manual field '
'specification to automatic field '
'numbering')
field_name = str(auto_arg_index)
auto_arg_index += 1
elif field_name.isdigit():
if auto_arg_index:
raise ValueError('cannot switch from manual field '
'specification to automatic field '
'numbering')
# disable auto arg incrementing, if it gets
# used later on, then an exception will be raised
auto_arg_index = False
# given the field_name, find the object it references
# and the argument it came from
obj, arg_used = self.get_field(field_name, args, kwargs)
@ -195,7 +213,8 @@ class Formatter:
# expand the format spec, if needed
format_spec = self._vformat(format_spec, args, kwargs,
used_args, recursion_depth-1)
used_args, recursion_depth-1,
auto_arg_index=auto_arg_index)
# format the object and append to the result
result.append(self.format_field(obj, format_spec))