Format String: Only when value supplied

[Ned Batchelder]

On 6/24/14 5:18 AM, Florian Lindner wrote:
> Hello,
>
> I have a format string like:
>
>   print "{:10} {:25} = {:6}   ({})".format(mod, name, value, description)
>
> description can be None. In this case I want to print an empty string (which
> can be achieved by replacing it with 'description or ""') and I want to omit
> the brackets. Is there a way to tell the format string to omit a part if an
> input variable is None?

.format() is not that sophisticated.  One option is to build your string 
in pieces like this:

     if description:
         nice_description = "   ({})".format(description)
     else:
         nice_description = ""
     print "{:10} {:25} = {:6}{}".format(mod, name, value, nice_description)

Another option is to use a real templating engine like Mako or Jinja 
that lets you use conditionals.

>
> Another question: value can be bool. When I format value with just {} if
> prints True or False, when I use {:6} it prints 1 or 0. Is there a way to
> get pack to True / False?

You can force it to be a string  with "{!s:6}"

-- 
Ned Batchelder, http://nedbatchelder.com