How to append numpy arrays to txt file-CodePudding

There are a list of image files I want to convert to numpy arrays and append them to a txt file, each array line after line. This is my code:

from PIL import Image
import numpy as np
import os

data = os.listdir("inputs")
print(len(data))

with open('np_arrays.txt', 'a ') as file:
    for dt in data:
        img = Image.open("inputs\\"   dt)
        np_img = np.array(img)
        file.write(np_img)
        file.write('\n')

but file.write() requires a string and does not accept a numpy ndarray. How can I solve this?

CodePudding user response：

The write() function only allows strings as its input. Try using numpy.array2string.

CodePudding user response：

Numpy also allows you to save directly to .txt files with np.savetxt. I'm still not entirely sure what format you want your text file to be in but a solution might be something like:

from PIL import Image
import numpy as np
import os

data = os.listdir("inputs")
print(len(data))

shape = ( len(data), .., .., ) # input the desired shape

np_imgs = np.empty(shape)

for i, dt in enumerate(data):
    img = Image.open("inputs\\"   dt)
    np_imgs[i] = np.array(img) # a caveat here is that all images should be of the exact same shape, to fit nicely in a numpy array

np.savetxt('np_arrays.txt', np_imgs)

Note that np.savetxt() has a lot of parameters that allow you to finetune the outputted txt file.