Add integer to an array in Python

Question

I am trying to add an integer to an array but I am getting an error. Here is my code:

import numpy as np
import h5py

for i in range(1, 621):
    with h5py.File("C:\\A" + str(i) + ".out") as f:
        data = np.array(f['rxs']['rx1']['Ey'])
        data.append(0)
    np.savetxt("C:\\A" + str(i) + ".csv", data, delimiter = ",")

For this I keep getting an error saying: "AttributeError: 'numpy.ndarray' object has no attribute 'append'"

I have also tried concatenate with an array consisting just 1 integer but it doesn't work. I used these lines for that:

data = np.array(f['rxs']['rx1']['Ey'])
b = np.array([[0]])
np.concatenate(data, b)

I get this error for this one: "TypeError: only integer scalar arrays can be converted to a scalar index"

The original aim of my code is to convert HDF files to CSV files which works if I don't try to change the array.

Could you please help?

Be aware that np.append is inefficient as it always creates and returns a modified copy of the array. The original array isn't modified. — Michael Butscher
– Michael Butscher, Commented Feb 1, 2019 at 12:48
@MichaelButscher: Unless you store the result in the same array name — Sheldore
– Sheldore, Commented Feb 1, 2019 at 12:49
@Bazingaa But even then first a new array has to be allocated, data of previous array copied and finally the previous array deleted. For a Python list.append this happens only sometimes. — Michael Butscher
– Michael Butscher, Commented Feb 1, 2019 at 12:51
@MichaelButscher: So what are the situations when np.append should be used and when should it be avoided? — Sheldore
– Sheldore, Commented Feb 1, 2019 at 12:55

Edgar H · Accepted Answer · 2019-02-01 12:50:36Z

4

You are not dealing with a python list but a numpy array.

To solve the problem at hand you can use numpy.append

data = np.append(data, 0)

You can also not create a numpy array to begin with. What is the type of f['rxs']['rx1']['Ey']? (You can find out with print(type(f['rxs']['rx1']['Ey'])))

if it is a list, you can simply do

data = f['rxs']['rx1']['Ey']
data.append(0)

edited Feb 1, 2019 at 12:50

answered Feb 1, 2019 at 12:48

Edgar H

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2 Comments

Edgar H Over a year ago

Updated the answer with another suggestion. Accept the answer if it resolves your issue so other people do not look at the question

Toykan Ozdeger Over a year ago

It says "<class 'h5py._hl.dataset.Dataset'>". But your answer solved my problem. Thanks!

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