from decimal import Decimal
a1 = 0.00000999
a2 = 13400
b1 = a1*a2
print(b1) # 0.13386599999999999
a1=Decimal(0.00000999)
a2=Decimal(13400)
b1 = a1*a2
print(b1)  #0.1338659999999999895440921591
a1=Decimal(str(0.00000999))
a2=Decimal(str(13400))
b1 = a1*a2
print(b1) #0.13386600   正确

#注意用Decimal函数，需要用str()函数转成字符型