如何在Python中检查某些东西是否是x折叠?

时间:2017-11-26 20:47:53

标签: python

所以,我正在努力制作这个节目,我现在非常接近,但我无法完成最后的工作。我追踪了我的问题,因为问题在于使用模数。我试图获得五倍的e,但是当我这样做时,我的列表中的第三个元素得到-2,这不是我期望的。

这可能是因为我试图用模数除去负数,但我无法解决问题,因为我不知道如何解决问题。有人可以帮帮我吗?

def f10(start, n):
    """
    The parameters start and n are both int's. Furthermore n > 0.
    The function f10() should return a list of int's that contains n
    elements.
    The first element (e) in the resulting list has to be start.
    The successor of an element e is calculated as follows:
    - if e is a fivefold (e.g. n is divisible by 5),
      then the next value of e is e / 5
    - if e is not a fivefold, then the next value of e is e - 4

    Example:
        f10(1, 10) should return
        [1, -3, -7, -11, -15, -3, -7, -11, -15, -3]
        f10(9, 12) should return
        [9, 5, 1, -3, -7, -11, -15, -3, -7, -11, -15, -3]
    """

    pass

    new_list = []
    k = range(start, n+1)
    e = k[0]

    new_list.append(e)

    for e in k:
        if e % 5 == 0:
            e = float(e) / 5
        else:
            e -= 4

        new_list.append(e)

    return new_list

print f10(1, 10)
print f10(9, 12)

所以,我应该得到:

[1, -3, -7, -11, -15, -3, -7, -11, -15, -3]

但是我得到了

[1, -3, -2, -1, 0, 1.0, 2, 3, 4, 5, 2.0]

非常感谢帮助。

2 个答案:

答案 0 :(得分:1)

这里有一些问题。最重要的是,您尝试使用变量e来迭代循环并存储计算结果。

试试这个:

def f10(start, n):
    x = start
    new_list = []
    for i in range(n):
        new_list.append(x)
        x = x-4 if x%5 else x//5
    return new_list

答案 1 :(得分:1)

您必须使用以前的值来计算新值。

def f10(start, n):

    result = [start] # I put first element

    for _ in range(n-1): # I have to put other n-1 elements yet
        if start % 5 == 0:
            start //= 5
        else:
            start -= 4

        result.append(start)

    return result

# --- compare result with expected list ---

print(f10(1, 10) == [1, -3, -7, -11, -15, -3, -7, -11, -15, -3])
# True

print(f10(9, 12) == [9, 5, 1, -3, -7, -11, -15, -3, -7, -11, -15, -3])
# True

编辑:如果您不想range(),那么您可以使用while len(result) < n:

def f10(start, n):

    result = [start]

    while len(result) < n:
        if start % 5 == 0:
            start //= 5
        else:
            start -= 4

        result.append(start)

    return result