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To make the for loop pause until we receive a signal for the next item, we can use a synchronization mechanism such as a semaphore or a condition variable.

With a semaphore, we can initialize it with a value of 0 and call its wait() method at the end of each iteration of the loop. This will cause the loop to block until another thread or process signals the semaphore to increase its value, allowing the loop to continue to the next item.

Example code using a semaphore:

import threading

items = [1, 2, 3, 4, 5]
semaphore = threading.Semaphore(0)

for item in items:
    # process item here
    # ...

    semaphore.acquire()  # pause loop until signal is received

To signal the semaphore to release, we can call its release() method from another thread or process:

semaphore.release()  # signal loop to continue to next item

Alternatively, we can use a condition variable to achieve a similar effect. We can create a condition variable and call its wait() method at the end of each iteration of the loop. This will block the loop until another thread or process calls the notify() or notify_all() method on the same condition variable.

Example code using a condition variable:

import threading

items = [1, 2, 3, 4, 5]
condition = threading.Condition()

for item in items:
    # process item here
    # ...

    with condition:
        condition.wait()  # pause loop until signal is received

To signal the condition variable to release, we can call its notify() or notify_all() method from another thread or process:

with condition:
    condition.notify()  # signal loop to continue to next item