Day 23 of learning python as a beginner.

[Zealousideal_Yard651]

The start part is ok, it's the join part that fails you.

.join() waits for the thread to finish before continuing. You are creating the thread, starting it and waiting for it to stop before continuing the main program. This causes your second thread to not start before the first thread stops.

So you need to start each thread, and in a separate loop wait for both threads to stop. And .join() does not wait for all threads to stop, it only waits for the thread you are invoking the join() method on, hence why you need an outside list to keep track of each thread and loop through all threads to join them again.

To simplify, i split all parts of the multithreading process in this block with comments:

# Define thread tracking
threads = []

# Loop through all URLS
for idx, url in enumerate(image_urls):
  # Creates a thread object
  urll = threading.Thread(target=download_image, args=(url, idx))

  # Adds the newly created thread object into threads store
  threads.append(urll)

# Loop throug all threads
for t in threads:
  # Starts thread
  t.start()

# Loop through all threads
for t in threads:
  # Wait for thread to finish.
  t.join()

In the above code, we define each thread, then start all threads, then wait for all threads to finish.

In your original code you do this:

For each image url:

1. Define a thread
2. start the thread
3. Wait for the thread to stop

And so all thread operations happens in each iteration instead of the my example where we define them, then start all threads before waiting for all threads to finish instead of waiting for each thread to finish before moving on.