why numpy.ndarray is object is not callable in my simple for python loop

Question

I loaded a text file containing a two column matrix (eg below)

[ 1   3
  2   4
  3   5 
  2   0]

My calculation is just to sum each row ie 1+3, 2+4, 3+5 and 2+0. I am using the below code:

data=np.loadtxt(fname="textfile.txt")## to load the above two column
xy= data
for XY in xy:
   i=0  
   Z=XY(i,0)+XY(i,1)
   i=i+1      
   print (Z)

But I received an error saying numpy.ndarray object is not callable . Why does this happen? How can I do this simple calculation? Thanks.

Answer 1

The error TypeError: 'numpy.ndarray' object is not callable means that you tried to call a numpy array as a function.

Use

Z=XY[0]+XY[1]

Instead of

Z=XY(i,0)+XY(i,1)

Answer 2

Sometimes, when a function name and a variable name to which the return of the function is stored are same, the error is shown. Just happened to me.

Answer 3

Avoid loops. What you want to do is:

import numpy as np
data=np.loadtxt(fname="data.txt")## to load the above two column
print data
print data.sum(axis=1)

Answer 4

Avoid the for loop for XY in xy: Instead read up how the numpy arrays are indexed and handled.

Numpy Indexing

Also try and avoid .txt files if you are dealing with matrices. Try to use .csv or .npy files, and use Pandas dataframework to load them just for clarity.

Answer 5

Not for the example asked above but sometimes this error happens because you forget to specify brackets [] instead of parenthesis for your numpy.ndarray. Such as writing arr(x,y) in a for loop that explores x and y in arr instead of its correct form: arr[x,y].