Issue #13598: Add auto-numbering of replacement fields to string.Formatter.
diff --git a/Lib/string.py b/Lib/string.py
index b57c79b..72a09f7 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -169,7 +169,8 @@
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 @@
# 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 @@
# 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))