gil_vs_threads.py

'''
  Run as 
  > python3 gil_vs_threads.py  2> /dev/null
'''

import threading
import sys

the_value = 0

def do_read_update(input_output):
    global the_value
    # Read
    old_value = the_value

    if input_output:
        sys.stderr.write('.')
        sys.stderr.flush()

    # Modify
    the_value = old_value + 1

def thread_func(input_output):
    for _ in range(1000):
        do_read_update(input_output)
        
        
if __name__ == '__main__':
    input_output = True

    print("Creating threads")
    threads = [ threading.Thread(target=thread_func, args=(input_output,)) for _ in range(100)]

    print("Starting threads")
    for t in threads:
        t.start()
        
    print("Waiting threads")
    for t in threads:
        t.join()
        
    print("Final value:", the_value)