Google Colab reading files from colabdisk instead of upload

Question

I've got a function that only works with colab.upload not with passing it a filename from a file on the colab disk, I uploaded from Drive. I want to work with a jpg picture for the TensorFlow object detection API.

This is working:

uploaded = files.upload()
img_infer = list(uploaded)[0]

print('running test on: ' + img_infer)
img_inference(img_infer)

but not this:

for file in os.listdir("/content/test"):
    print('running test on: ' + file)
    img_infer = list(file)[0]
    img_inference(img_infer)

Error:

---------------------------------------------------------------------------

FileNotFoundError                         Traceback (most recent call last)

<ipython-input-31-4fbcedf7108a> in <module>()
     12   print('Teste mit Bild: ' + file)
     13   img_infer = list(file)[0]
---> 14   img_inference(img_infer)

2 frames

<ipython-input-8-6a0800ccaf6f> in img_inference(img_path)
     50 
     51 def img_inference(img_path):
---> 52   image = read_image_bgr(img_infer)
     53 
     54   # copy to draw on

/content/keras-retinanet/keras_retinanet/utils/image.py in read_image_bgr(path)
     30     """
     31     # We deliberately don't use cv2.imread here, since it gives no feedback on errors while reading the image.
---> 32     image = np.asarray(Image.open(path).convert('RGB'))
     33     return image[:, :, ::-1].copy()
     34 

/usr/local/lib/python3.6/dist-packages/PIL/Image.py in open(fp, mode)
   2528 
   2529     if filename:
-> 2530         fp = builtins.open(filename, "rb")
   2531         exclusive_fp = True
   2532 

FileNotFoundError: [Errno 2] No such file or directory: 'I'

Answer 1

There is a logic problem in your code:

for file in os.listdir("/content/test"):
  print('running test on: ' + file)
  img_infer = list(file)[0] # <== This line is not correct
  img_inference(img_infer)

You have to change img_infer = list(file)[0] to img_infer = file, or just delete img_infer = list(file)[0] and change img_inference(img_infer) to img_inference(file).

In other words:

for file in os.listdir("/content/test"):
  print('running test on: ' + file)
  img_inference(file)

---

To further explain what is happening in your original code, suppose /content/test contains aaa.txt, bbb.py, ccc.jpg. Then:

for file in os.listdir("/content/test"):
  # In the first iteration file == "aaa.txt"
  print('running test on: ' + file)
  # But then list(file) == ["a", "a", "a", ".", "t", "x", "t"] which is not what you want.
  # And then list(file)[0] == "a", therefore img_infer == "a"
  img_infer = list(file)[0]
  img_inference(img_infer)

Hope it helps!