I loaded a text file containing a two column matrix (e.g. below)

```
[ 1 3
2 4
3 5
2 0]
```

My calculation is just to sum each row i.e. 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.

### 4 Answers

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)
```

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)
```

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.

Avoid the for loop`for XY in xy:`

Instead read up how the numpy arrays are indexed and handled.

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.