sign function

[kedlaya]

Should the following function exist globally?

def sign(x):
    if x > 0:
        return 1
    if x < 0:
        return -1
    return 0

I'm not sure if this is identical to

def sign(x):
    return x.__cmp__(0)

I'm also ambivalent as to whether this function is called "sign", "signum", or "sgn".