python - 根据python中的变量限制小数

Question

我正在尝试编写一个返回 golden ratio 的程序最多小数位。我到目前为止是这样的:

def gr(n):
    a, b = 0, 1
    for x in range(0, n):
        a, b = b, a+b
    else:
        return(a)

    decimals = int(input("What amount of decimals do you want to see of the golden ratio?"))
    ratio = gr(41)/gr(40)
    print(format(ratio, '2f'))

问题是我找不到一种方法来将ratio 格式化为decimals 中的数字。

Answer 1

将精度/小数变量传递给 str.format:

decimals = int(input("What amount of decimals do you want to see of the golden ratio?"))
ratio = gr(41)/gr(40)
print("{:.{}f}".format(ratio,decimals))

例子:

In [3]: decimals = int(input("What amount of decimals do you want to see of the golden ratio?"))
What amount of decimals do you want to see of the golden ratio?5

In [4]: ratio = gr(41)/gr(40)

In [5]: print("{:.{}f}".format(ratio,decimals))
1.61803