[Python-Dev] The syntax of replacement fields in format strings (original) (raw)
Serhiy Storchaka storchaka at gmail.com
Tue Oct 31 06:37:27 EDT 2017
- Previous message (by thread): [Python-Dev] Convert Sqlite Function from cx_Oracle
- Next message (by thread): [Python-Dev] The syntax of replacement fields in format strings
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]
According to the specification of format string syntax [1] (I meant str.format(), not f-strings), both argument name and attribute name must be Python identifiers.
But the current implementation is more lenient and allow arbitrary sequences of characters while they don't contain '.', '[', ']', '{', '}', ':', '!'.
'{#}'.format_map({'#': 42}) '42' import types '{0.#}'.format(types.SimpleNamespace(**{'#': 42})) '42'
This can be confusing due to similarity with the format string syntaxes in str.format() and f-strings.
name = 'abc'
f'{name.upper()}' 'ABC' '{name.upper()}'.format(name='abc') Traceback (most recent call last): File "", line 1, in AttributeError: 'str' object has no attribute 'upper()'
If accept only identifiers, we could produce more specific error message.
Is there a bug in the documentation or in the implementation?
[1] https://docs.python.org/3/library/string.html#format-string-syntax
- Previous message (by thread): [Python-Dev] Convert Sqlite Function from cx_Oracle
- Next message (by thread): [Python-Dev] The syntax of replacement fields in format strings
- Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]