类型错误:p_vinet()接受两个位置参数，但给出了4个。

I am trying to pass arguments to a function and I think I'm doing it correctly but it still gives the error: TypeError: p_vinet() takes 2 positional arguments but 4 were given

我试图将参数传递给函数，我认为我做的是正确的，但它仍然给出了错误:TypeError: p_vinet()接受了两个位置参数，但给出了4个。

Here's the pieces of my code first and then I'll give the part that gives the error.

这是我的代码片段，然后我会给出错误的部分。

volumeMgO is a previously calculated array consisting of:

volumeMgO是一个之前计算过的数组，包括:

array([ 7.64798549,  7.67153344,  7.67153344,  7.8068763 ,  7.97288941,
8.14781986,  8.33321177,  8.53118834,  8.74433596,  8.97545339,
9.22826581,  9.50740563,  9.81962839])

params_MgO is this:

params_MgO是这样的:

params_MgO    = [11.244, 160., 4.0]

The vinet function is:

vinet函数是:

def p_vinet(v, params):
  """
  This function will calculate pressure from Vinet equation.

  Parameters
  ==========
  v = volume
  params = [V0, K0, K0']

  Returns
  =======
  Pressure calculated from Vinet equation
  """
  f_v = np.power( v/params[0], 1./3.)
  eta = 1.5 * (params[2] - 1.)

  P = 3 * params[1] * ((1 - f_v) / np.power(f_v, 2) ) * np.exp(eta * (1 - 
  f_v))

  return P

Finally, the slope function is just a simple way of taking a derivative:

最后，斜率函数是求导的简单方法:

def slope(func, x, h, args=()):
  """
  find a slope for function f at point x

  Parameters
  =========
  f = function
  x = independent variable for f
  h = distance along x to the neighboring points

  Returns
  =======
  slope
  """

  rise = func(x+h, *args) - func(x-h, *args)
  run = 2.*h

  s = rise/run

  return s

Now here is where the issue comes. When I type:

现在问题来了。当我类型:

BulkModulus_MgO = np.zeros(volumeMgO.size)
for i in range(volumeMgO.size):
   BulkModulus_MgO[i] = slope(p_vinet, volumeMgO[i], volumeMgO[i]*0.0001, 
   args=(params_MgO)) 

I get this error:

我得到这个错误:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-116-60467d989bbc> in <module>()
  1 BulkModulus_MgO = np.zeros(volumeMgO.size)
  2 for i in range(volumeMgO.size):
----> 3     BulkModulus_MgO[i] = slope(p_vinet, volumeMgO[i], 
volumeMgO[i]*0.0001, args=(params_MgO))

<ipython-input-100-618f25e85d34> in slope(func, x, h, args)
 15     """
 16 
---> 17     rise = func(x+h, *args) - func(x-h, *args)
 18     run = 2.*h
 19 

TypeError: p_vinet() takes 2 positional arguments but 4 were given

I don't get it. p_vinet needs arguments v and params, and I supply v through the x+h and x-h in the slope function, and the params is a list with 3 entries that p_vinet unpacks. So that's 2 arguments. Why is it saying I'm supplying 4?

我不明白。p_vinet需要参数v和params，在斜率函数中我提供v通过x+h和x-h，而params是一个包含3个p_vinet解包的列表。这是两个参数。为什么说我供应4?

Sorry if it's slightly confusing how I'm presenting the code. I'm coding in jupyter notebook and all the functions are separate. volumeMgO is calculated separately from previous code with no issues.

不好意思，如果这有点让人困惑我是怎么呈现代码的。我在jupyter笔记本上编码，所有的功能都是分开的。volumeMgO是与以前的代码分开计算的，没有问题。

1 个解决方案

#1

Let's look at this line of code:

让我们看看这行代码:

BulkModulus_MgO[i] = slope(p_vinet, volumeMgO[i], volumeMgO[i]*0.0001, 
   args=(params_MgO))

args should be like this: args=(params_MgO,) (tuple with one element in it) instead of args=(params_MgO) (not tuple, just array of 3 elements) because in second case unpacking *args in slope() function gives you 3 additional arguments (each element of params_MgO). That's why you got 4 arguments in slope() function. In first case unpacking gives you entire array as single parameter (like params in p_vinet() function).

args应该是这样的:args=(params_MgO)，而不是args=(params_MgO)(不是tuple，而是3个元素的数组)，因为在第二个case中，unpacking *args在slope()函数中提供了3个附加参数(params_MgO的每个元素)。这就是斜率()函数中有4个参数的原因。在第一种情况下，unpacking将整个数组作为单个参数(如p_vinet()函数中的params)。