python precision calculation

calculation.py

def yuan2fen(amount):
    if isinstance(amount, str):
        amount = float(amount)

    a = amount * 100

    z = str(a).split(".")
    if len(z) == 2:
        if int(z[1][0]) > 4:
            return int(a) + (1 if a > 0 else -1)
        else:
            return int(a)
    else:
        return int(a)

      
def yuan2fen2(amount):
    if isinstance(amount, str):
        amount = float(amount)
    a = int(amount * 1000)
    l = a % 10
    s1 = 1 if l > 4 else 0
    s = int(a / 10) + (s1 if a > 0 else -s1)
    return s

if __name__ == '__main__':
    assert yuan2fen(38.91) == 3891
    assert yuan2fen(38.915) == 3892
    assert yuan2fen(0.915) == 92
    assert yuan2fen(.915) == 92
    assert yuan2fen(38.9) == 3890
    assert yuan2fen(38.) == 3800
    assert yuan2fen(-38.) == -3800
    assert yuan2fen(120000000000000) == 12000000000000000
    assert yuan2fen(-120000000000000) == -12000000000000000
    assert yuan2fen(0) == 0
    assert yuan2fen(.0) == 0
    assert yuan2fen(.004) == 0
    assert yuan2fen(.005) == 1
    assert yuan2fen(-.005) == -1
    assert yuan2fen(-0.005) == -1
    assert yuan2fen(0.005) == 1