Error: unsupported operand type(s) for ** or pow(): 'tuple' and 'int'

Question

I'm traying to write a code that have r_1 and r_2 are vectors and the other parameters are float. I got this error and i don't know why ! i think the problem in type of n_1 or n_H

import numpy as np
from numpy import *
#import math
r_1=[]
for i in range(3):
    v=input("Elemnts1:  ")
    r_1 = append(r_1,v)
print(r_1)
r_2=[]
for i in range(3):
    v=input("Elemnts2:  ")
    r_2 = append(r_2,v)
print(r_2)
Delta_theta=float(input("Delta_theta="))
t_1=float(input("t_1="))
t_2=float(input("t_2=")) 
Delta_t= t_2 - t_1

def orbit_determination(r_1,r_2,Delta_theta,Delta_t):
    mu=398600.0
    m=(mu*(Delta_t)**2)/(2*np.sqrt(np.dot(r_1,r_2))*np.cos(Delta_theta/2))**3
    L_1= (r_1+r_2)/4*np.sqrt(np.dot(r_1,r_2))*np.cos(Delta_theta/2)
    L= L_1 -(1/2)
    n_H=(12/22)+(10/22)*np.sqrt(1+((44*m)/9*(L+(5/6))))
    n_1=n_H+0.1
#compute the Semi-parameter from
    p=(n_1**2)*np.cross((r_1,r_2)**2)/mu*((Delta_t)**2)


 File "orbit_determinition11.py", line 51, in <module>
    orbit_determination(r_1,r_2,Delta_theta,Delta_t)
  File "orbit_determinition11.py", line 27, in orbit_determination
    p=(n_1**2)*np.cross((r_1,r_2)**2)/mu*((Delta_t)**2)
TypeError: unsupported operand type(s) for ** or pow(): 'tuple' and 'int'

Answer 1

When declaring float numbers, you need to use . , so when you introduce a number in the variables you need to make sure that the format is 2.3 and not 2,3 , otherwise you are declaring a tuple.

Answer 2

maybe you should add p = int(p) before line 27. I guess it might work.

Answer 3

As Matthias hints to in a comment

So what do you expect (r_1,r_2)**2 to do?

The problem is on the line

p=(n_1**2)*np.cross((r_1,r_2)**2)/mu*((Delta_t)**2)

specifically

np.cross((r_1,r_2)**2)

As you're calling np.cross which

Return the cross product of two (arrays of) vectors.

Returns c: ndarray

Vector cross product(s).

The argument you're passing it is (r_1,r_2)**2 which constructs a tuple of the r_1 and r_2 vectors and attempts to raise it to the power of two (which isn't supported), which is why you're getting

 File "orbit_determinition11.py", line 27, in orbit_determination p=(n_1**2)*np.cross((r_1,r_2)**2)/mu*((Delta_t)**2) TypeError: unsupported operand type(s) for ** or pow(): 'tuple' and 'int'

---

It looks like n_1 , mu , and Delta_t are floats - though it's not clear from your code what you're trying to do and what p is supposed to be:

If p is a vector, possibly the **2 is a typo:

p=(n_1**2)*np.cross(r_1,r_2)/mu*((Delta_t)**2)

If p is a float, possibly np.dot was meant:

p=(n_1**2)*((np.dot(r_1,r_2))**2)/mu*((Delta_t)**2)