Writing a 3D Numpy array to a CSV file

Question

I have a 3D Numpy array with the shape [1953,949,13]. I want to write it to a CSV file where each row should contain a 2D array of shape [949 13] and csv file should contain 1953 rows. I tried np.savetext and it supports only 1D and 2D arrays. Then I tried line by line writing to a CSV but it requires each matrix to be converted to a string. How can I get this done in python? My requirement is different from the question Storing values in a 3D array to csv

Answer 1

I'm not sure if it's the best way to doing it, but I faced the same problem and here's how I solved it.

import csv
import numpy as np
fil_name = 'file'
example = np.zeros((2,3,4))
example = example.tolist()
with open(fil_name+'.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile, delimiter=',')
    writer.writerows(example)

#to read file you saved
with open(fil_name+'.csv', 'r') as f:
  reader = csv.reader(f)
  examples = list(reader)

print(examples)
nwexamples = []
for row in examples:
    nwrow = []
    for r in row:
        nwrow.append(eval(r))
    nwexamples.append(nwrow)
print(nwexamples)

Answer 2

I used this method instead, not aware of any better method:

# reshaping the array from 3D matrice to 2D matrice.
arrReshaped = arr.reshape(arr.shape[0], -1)
# saving reshaped array to file.
np.savetxt(filename, arrReshaped)
# retrieving data from file.
loadedArr = np.loadtxt(filename)
# This loadedArr is a 2D array, therefore we need to convert it to the original array shape.
# reshaping to get original matrice with original shape.
loadedOriginal = loadedArr.reshape(loadedArr.shape[0], loadedArr.shape[1] // arr.shape[2], arr.shape[2])