New submission from Paul McMillan <p...@mcmillan.ws>: In Python 2.7, I can use an empty format string to indicate automatically numbered positional arguments when formatting the builtin string object.
http://docs.python.org/release/2.7/library/string.html#format-string-syntax If I subclass string.Formatter, this expected functionality doesn't work. http://docs.python.org/release/2.7/library/string.html#string-formatting Python 2.7.2+ (default, Oct 4 2011, 20:06:09) [GCC 4.6.1] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> from string import Formatter >>> class MyFormatter(Formatter): ... pass ... >>> fs_a = 'a{0}b{1}c' >>> fs_b = 'a{}b{}c' >>> fs_a.format(1, 2) 'a1b2c' >>> fs_b.format(1, 2) 'a1b2c' >>> fmt = MyFormatter() >>> fmt.format(fs_a, 1, 2) 'a1b2c' >>> fmt.format(fs_b, 1, 2) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/string.py", line 545, in format return self.vformat(format_string, args, kwargs) File "/usr/lib/python2.7/string.py", line 549, in vformat result = self._vformat(format_string, args, kwargs, used_args, 2) File "/usr/lib/python2.7/string.py", line 571, in _vformat obj, arg_used = self.get_field(field_name, args, kwargs) File "/usr/lib/python2.7/string.py", line 632, in get_field obj = self.get_value(first, args, kwargs) File "/usr/lib/python2.7/string.py", line 591, in get_value return kwargs[key] KeyError: '' ---------- messages: 155708 nosy: PaulMcMillan priority: normal severity: normal status: open title: Custom string formatter doesn't work like builtin str.format versions: Python 2.7 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue14297> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
