Will I ever understand threads in Python?

Question

Python

We have the following test code:

import threading
import random

lock = threading.BoundedSemaphore(value=5)

def write(*args, **kwargs):
    global lock
    lock.acquire()
    print "Thread name: %s. Result %-6f" % (args)
    lock.release()

class App(threading.Thread):
    
    def __init__(self, *args, **kwargs):
        threading.Thread.__init__(self, *args, **kwargs)
    
    def run(self):
        for i in xrange(5000):
            r = random.random()
            i = i*i-789*96/2*r
        write(self.name, i)
 
for i in xrange(5):
    app = App(name="THREADING_%d" % (i))
    app.start()

Well, everything is fine, but the feeling that the locks do not work. The screenshot shows that the lines in the console get uneven. It should be?

Answer 1

And here is what you need:

import threading
import random

lock = threading.RLock() # <<< one

def write(*args, **kwargs):
    global lock
    with lock: # <<< two
        print "Thread name: %s. Result %-6f" % (args)

class App(threading.Thread):
    
    def __init__(self, *args, **kwargs):
        threading.Thread.__init__(self, *args, **kwargs)
        self.setDaemon(False)
    
    def run(self):
        for i in xrange(5000):
            r = random.random()
            i = i*i-789*96/2*r
        write(self.name, i)
        


for i in xrange(5):
    app = App(name="THREADING_%d" % (i))
    app.start()

Answer 2

Yes, it is normal