在 Python 中，如何在函数中定义任意数量的索引变量？

Question

First off, thank you in advance for bearing with my novice understanding of Python. I am coming from MATLAB so hopefully that gives some context.

In MATLAB I define a mathematical function as:

f =@ (x) 2*x(1)^2 + 4*x(2)^3

In Python, I wrote:

def f(x):
   return 2*x(1)**2 + 4*x(2)**3

But I get an error inside my other function (finite difference method for creating gradient vector):

line 9, in f
    return 2*x(1)**2 + 4*x(2)**3
TypeError: 'numpy.ndarray' object is not callable

(an input X1 that contains n-number of entries, specified by the number of variables in the original equation, is fed back into the function f(x) to evaluate at a specific point).

I am happy to share the code I have written so far (or the working code in MATLAB) for reference, but the main thing I am wondering is how I can create an arbitrary number of variables for an equation like I do in MATLAB with x(1),x(2)...x(n).

Answer 1

Array indexing in Python is done with square brackets, not parentheses. And remember that Python starts in indices at 0, not 1.

def f(x):
    return  2*x[0]**2 + 4*x[1]**3

Answer 2

Your function is called f but you are trying to call x(2) . You get the error because you are trying to call x as a function, but x is a numpy array