Python: Capitalize a word using string.format()

Question

Is it possible to capitalize a word using string formatting? For example,

\"{user} did such and such.\".format(user=\"foobar\")

should return \

Answer 1

As said @IgnacioVazquez-Abrams, create a subclass of string.Formatter allow you to extend/change the format string processing.

In your case, you have to overload the method convert_field

from string import Formatter
class ExtendedFormatter(Formatter):
    """An extended format string formatter

    Formatter with extended conversion symbol
    """
    def convert_field(self, value, conversion):
        """ Extend conversion symbol
        Following additional symbol has been added
        * l: convert to string and low case
        * u: convert to string and up case

        default are:
        * s: convert with str()
        * r: convert with repr()
        * a: convert with ascii()
        """

        if conversion == "u":
            return str(value).upper()
        elif conversion == "l":
            return str(value).lower()
        # Do the default conversion or raise error if no matching conversion found
        return super(ExtendedFormatter, self).convert_field(value, conversion)

# Test this code

myformatter = ExtendedFormatter()

template_str = "normal:{test}, upcase:{test!u}, lowcase:{test!l}"


output = myformatter.format(template_str, test="DiDaDoDu")
print(output)