py23.py 文件源码

def isclose(a, b, rel_tol=1e-09, abs_tol=0):
        """
        Python 2 implementation of Python 3.5 math.isclose()
        https://hg.python.org/cpython/file/v3.5.2/Modules/mathmodule.c#l1993
        """
        # sanity check on the inputs
        if rel_tol < 0 or abs_tol < 0:
            raise ValueError("tolerances must be non-negative")
        # short circuit exact equality -- needed to catch two infinities of
        # the same sign. And perhaps speeds things up a bit sometimes.
        if a == b:
            return True
        # This catches the case of two infinities of opposite sign, or
        # one infinity and one finite number. Two infinities of opposite
        # sign would otherwise have an infinite relative tolerance.
        # Two infinities of the same sign are caught by the equality check
        # above.
        if _isinf(a) or _isinf(b):
            return False
        # Cast to float to allow decimal.Decimal arguments
        if not isinstance(a, float):
            a = float(a)
        if not isinstance(b, float):
            b = float(b)
        # now do the regular computation
        # this is essentially the "weak" test from the Boost library
        diff = _fabs(b - a)
        result = ((diff <= _fabs(rel_tol * a)) or
                  (diff <= _fabs(rel_tol * b)) or
                  (diff <= abs_tol))
        return result