Nick Coghlan wrote:
Eric Smith wrote:
So, is such a function desirable, and if so, where would it go? I could expose it through the string module, which is where the sort-of-related Formatter class lives.
string.parse_format and string.build_format perhaps? The inverse operation would be useful if you just wanted to do something like "use a default precision of 3" but otherwise leave things up to the original object.
def custom_format(fmt, value): details = string.parse_format(fmt) if details["precision"] is None: # Assumes None indicates missing details["precision"] = 3 fmt = string.build_format(details) return format(fmt, value)
return format(value, fmt) # ;-)
While having to rebuild and reparse the string is a little annoying,
yes
changing that would involve changing the spec for the __format__ magic method and I don't think we want to go there.
If parse_format were idempotent for its output like iter, then the change would, I think, be pretty minimal. I am assuming here that the __format__ method calls the parse_format(fmt) function that Eric proposed to expose. If details == parse_format(details) == parse_format(build_format(details)), then the rebuild and reparse is not needed and passing details instead of the rebuilt string should be transparent to __format__. tjr