Python Cookbook

Decorating an Object with Print-Like Methods

Credit: Jürgen Hermann

Problem

You want functionality similar to that of the print statement on a file object that is not necessarily standard output, and you want to access this functionality in an object-oriented manner.

Solution

Statement print is quite handy, but we can emulate (and optionally tweak) its semantics with nicer, object-oriented syntax by writing a suitable class:

class PrintDecorator:
    """ Add print-like methods to any writable file-like object. """

    def _ _init_ _(self, stream, do_softspace=1):
        """ Store away the stream for later use. """
        self.stream = stream
        self.do_softspace = do_softspace
        self.softspace = 0

    def Print(self, *args, **kw):
        """ Print all arguments as strings, separated by spaces.

            Take an optional "delim" keyword parameter to change the
            delimiting character and an optional "linend" keyword
            parameter to insert a line-termination string. Ignores
            unknown keyword parameters for simplicity.
        """
        delim = kw.get('delim', ' ')
        linend = kw.get('linend', '')
        if self.do_softspace and self.softspace and args: start = delim
        else: start = ''
        self.stream.write(start + delim.join(map(str, args)) + linend)
        self.softspace = not linend

    def PrintLn(self, *args, **kw):
        """ Just like self.Print(  ), but linend defaults to line-feed.
        """
        kw.setdefault('linend','\n')
        self.Print(*args, **kw) if _ _name_ _ == '_ _main_ _': # Here's how you use this: import sys out = PrintDecorator(sys.stdout) out.PrintLn(1, "+", 1, "is", 1+1) out.Print("Words", ...