Question

我一直试图将Python中的上一个和下一个数字相乘，但我总是得到一个不同的错误。这就是我一直在做的事情：

u=[1, 41, 56, 80]

def Filter(vel):
    global firstDerivative 
    firstDerivative = np.repeat(None, len(vel))
    for index, obj in enumerate(vel):
       if index !=0 & index !=len(vel-1):
           firstDerivative = (vel[index-1]*vel[index+1])/2

Filter(u)

出现以下错误：

TypeError: unsupported operand type(s) for -: 'list' and 'int'

我实际上也试过了地图，但是id没有用。

Answer 1

你需要从1迭代到-1，并在你去的时候填充firstDerivative数组：

def Filter(vel):
    global firstDerivative    # you are probably better advised to return firstDerivative instead
    firstDerivative = [0] * (len(vel) - 2)
    for ndx in range(1, len(vel) - 1):
        firstDerivative[ndx-1] = vel[ndx-1] * vel[ndx+1] / 2

firstDerivative = []        
u = [1, 2, 3, 4, 5, 6]
Filter(u)
firstDerivative

输出：

for firstderivative：

[1.5, 4.0, 7.5, 12.0]

Answer 2

自numpy被标记后，您只需使用a[:-2]*a[2:]/2：

即可

>>> import numpy as np
>>> a = np.array([1, 2, 3, 4, 5, 6])
>>> a[:-2]
array([1, 2, 3, 4])
>>> a[2:]
array([3, 4, 5, 6])
>>> a[:-2]*a[2:]/2
array([  1.5,   4. ,   7.5,  12. ])

请注意，它与衍生物无关。您应该更改代码或变量名称。衍生物将是差异，例如与(a[i+1] - a[i])/2：

>>> import numpy as np
>>> a = np.array([1, 2, 3, 4, 5, 6])
>>> (a[2:] - a[:-2])/2
array([ 1.,  1.,  1.,  1.])
>>> np.ediff1d(a)
array([1, 1, 1, 1, 1])

将Python中的上一个和下一个元素相乘

2 个答案:

输出：