switch-case

switch.py

_cache = {}


def case(x):
    if x not in _cache:
        _cache[x] = type("Case", (Exception,), {})
    return _cache[x]


def switch(x):
    raise case(x)


def binop(op, left, right):
    try: switch(op)

    except case("+"):
        return left + right

    except case("-"):
        return left - right

    except case("*"):
        return left * right

    except case("/"):
        return left / right

    except: # default
        raise ValueError("Unknown op %s" % op)


# In [1]: binop("*", 5, 6)
# Out[1]: 30

# In [2]: binop("/", 5, 6)
# Out[2]: 0.8333333333333334

# In [3]: binop("+", 5, 6)
# Out[3]: 11