Programming Python Utility Functions

Various Small Python Helpers

I’ve been working lately with arkon on various projects related to diStorm. One of these projects involved writing a solid Python API around an existing C API. This C API uses a lot of flags as arguments and return values of functions.
Since I want my code to be easy to use in an interactive shell, I’d like to return something that’s not just a number. The obvious solution is to use a Python Enum. There are many implementations going around, most of them equivalent. I’ve got the one I use. What I recently added though, is the SymbolInt:

def SymbolInt(value, name):
    class _SymbolInt(int):
        def __str__(self):
            return name
        def __repr__(self):
            return 'SymbolInt(%d, "%s")' % (value, name)
        def __eq__(self, other):
            if isinstance(other, str):
                other = other.lower()
            return int(self)==other or name.lower() == other
        def __ne__(self, other):
            return not self == other
    return _SymbolInt(value)

Short, and very much to the point, this makes exploratory API’s much more readable and usable. It is useful as a return value from enum functions as well.

Along with SymbolInt I wrote hexint:

class hexint(long):
    def __str__(self):
        return hex(self)[2:-1]
    __repr__ = __str__
    def __repr__(self):
        return hex(self)[:-1]

This one makes program addresses readable.

Lastly, here’s a little function that I found missing from itertools:

def head(iterable, num_items):
    for obj,i in zip(iterable,xrange(num_items)):
        yield obj

UPDATE: Don’t use this head() function, use itertools.islice instead. Thanks go to Erez for pointing that out.