A Python decorator for caching a function result on first call (e.g. for network requests). Works well with the property decorator.

CacheResult.py

from functools import wraps
from inspect import getargspec

def cacheResult(fn):
    cacheAttr = "{0}Cache".format(fn.__name__)
    argSpec = getargspec(fn)
    argNames = argSpec.args[1:]
    if len(argNames) > 1:
        raise RuntimeError("can't cache results if function takes multiple args")
    argName = argNames[0] if len(argNames) else None
    if argName:
        if argSpec.defaults:
            @wraps(fn)
            def wrapper(self, arg=argSpec.defaults[0]):
                if not hasattr(self, cacheAttr):
                    setattr(self, cacheAttr, {})
                cache = getattr(self, cacheAttr)
                if arg not in cache:
                    cache[arg] = fn(self, arg)
                return cache[arg]
        else:
            @wraps(fn)
            def wrapper(self, arg):
                if not hasattr(self, cacheAttr):
                    setattr(self, cacheAttr, {})
                cache = getattr(self, cacheAttr)
                if arg not in cache:
                    cache[arg] = fn(self, arg)
                return cache[arg]
    else:
        @wraps(fn)
        def wrapper(self):
            if not hasattr(self, cacheAttr):
                setattr(self, cacheAttr, fn(self))
            return getattr(self, cacheAttr)
    return wrapper