详解Python中的数据精度问题

print(1.1*2.2)

def multiple(m1, m2):
    r=''
    ## 若存在浮点型，则先转化为整数
    if type( m1 )==float or type( m2 )==float:
        print( "存在浮点数" )
        len_m1=len( str( m1 ).split( "." )[1] )
        len_m2=len( str( m2 ).split( "." )[1] )
        print( "m1的小数位：", len_m1 )
        print( "m2的小数位：", len_m2 )

        m1=int( 10**len_m1*m1 )
        m2=int( 10**len_m2*m2 )
        print( "m1化为整数：", m1 )
        print( "m2化为整数：", m2 )
        r=str( m1*m2 )
        print( "r：", r )

        l=len_m1+len_m2
        print( "l的总长度：", l )
        if l<len( r ):
            r_front=r[:-l]
            r_last=r[-l:]
            print( r_front, "-", r_last )
            r=r_front+"."+r_last
        else:
            r="0."+(l-len( r ))*"0"+r

    else:
        print( "不存在浮点数" )
        r=m1*m2
    return r

res = multiple(1.1,2.2)
print(res)

a1 = 0.235
a2 = round(a1,2)
a3 = '%.2f' % a1
print(a2)
print(a3)

from decimal import Decimal

a1 = 0.235
a2 = Decimal(str(a1)).quantize(Decimal("0.00"))
a3 = '{:.2f}'.fORMat(Decimal(str(a1)))
print(a2)
print(a3)