Inter Thread Communication With Condition() Method in Python - GeeksforGeeks

24 Jan, 2021
This article is based on how we use the Condition() method to implement Inter Thread Communication, let’s discuss this topic below -:
Let’s have some brief discussion on Inter Thread Communication before talking about Condition() implementation for inter-thread communication, When any thread required something from another they will organize communication between them, and with this communication, they will fulfill their requirement. It means that it is a process of communicating between the threads for any kind of requirement. 
We can say that the implementation of inter-thread communication using the condition() method is the up-gradation of that event object used for inter-thread communication. Here Condition represents some type of state change between threads like ‘send notification’, ‘got notification’.  See below how the condition object is creating:-     
Syntax :
condition_object = threading.condition( )
In this scenario, threads can wait for that condition and once that condition executes then threads can modify according to that condition. In simple word, we can say that the condition object gave access to threads to wait until another thread give notification to them. Condition object is always correlated with lock (RLock) concept internally.
Some following methods of Condition class we discuss below :
release()acquire()notify()wait()notifyAll()
release()
acquire()
notify()
wait()
notifyAll()
release() Method: When the need of the condition object is fulfilled by threads then we will use the release() method which helps us to free the condition object from their tasks and suddenly releases the internal lock which was obtained by the threads.
Syntax: condition_object.release()
acquire() Method: When we want to obtain or takeover any condition object for inter-threading communication then we always used acquire() method. The acquire() method is compulsory when we want to implement inter-thread communication using condition class. When we use this method suddenly threads obtain the internal lock system.
Syntax: condition_object.acquire()
notify() Method: When we want to send a notification to only one thread that is in waiting state then we always use notify() method. Here if one thread wants to be condition object up-gradation then notify() is used.
Syntax :condition_object.notify()                                      
wait(time) Method: The wait() method can be used to make a thread wait till the notification got and also till the given time will end. In simple words we can say that thread is to wait until the execution of the notify() method is not done. We can use time in it if we set a certain time then the execution will stop until time overs after that it will execute still the instructions are remaining.
Syntax: condition_object.wait()
Parameter:Time 
 notifyAll() Method: Here the notifyAll() method is used to send notifications for all waiting threads. If all threads are waiting for condition object updating then notifyAll() will use.
Syntax: condition_object.notifyAll()
Now let’s take a simple example to show how acquire and release methods are used and how they work through the entire program -:
Example 1:
Python3
# code# import modules  import threading import time  obj1= threading.Condition()    def task ():  obj1.acquire()  print('addition of 1 to 10 ')  add= 0  for i in range ( 1 , 11 ):    add = add+i  print(add)  obj1.release()  print('the condition object is releases now')      t1 = threading.Thread(target = task)t1.start()
addition of 1 to 10 
55
the condition object is releases now
In the above example, we use acquire() and release() method which can be used to obtain or acquire the condition object and after the completion of tasks releases the condition object. First, we are importing the required modules, and then we create the condition object which is obj1 then we create and start the thread t1, In the task named function there where we used acquire() method from these we obtain the condition object and also from here internal lock of threads are started. After the completion of instructions at the last we release the condition object and also the internal lock of threads is released.
Example 2:
In this example we used other methods to explain how they work through the entire program:-
Python3
# code  # import modules  import timefrom threading import *import random      class appointment:      def patient(self):    condition_object.acquire()    print('patient john waiting for appointment')    condition_object.wait()   # Thread is in waiting state    print('successfully got the appointment')    condition_object.release()    def doctor(self):    condition_object.acquire()    print('doctor jarry checking the time for appointment')    time=0     time=random.randint(1,13)    print('time checked')    print('oppointed time is {} PM'.format(time))    condition_object.notify()    condition_object.release()      condition_object = Condition()class_obj=appointment()  T1 = Thread(target=class_obj.patient)  T2 = Thread(target=class_obj.doctor)  T1.start()  T2.start()
patient john waiting for appointment
doctor jarry checking the time for appointment
time checked
oppointed time is 4 PM
successfully got the appointment
This is a simple example to explain the use of Condition() class and their methods in threading. Also, here we use an example of patient and doctor how patient and doctor first acquire the conditions and then how to notify them, and at last both also release the condition object. Let’s start first we create a class appointment which was having two functions which name as a patient() and doctor() and then we created two threads T1 and T2. With the help of the acquire() method, the doctor and patient both acquire the condition object in their first statement by this both the threads are internally locked. Now the patient has to wait for an appointment and got appointed after the execution of the wait() method doctor starting to check whether the time he chooses is it ok to go for an appointment or not and when the time is chosen by the doctor then it will notify to thread that is in waiting for the state by notify() method. Next after the notify() method, the patient got their notification and product both. Then after all this, both threads release the condition object by release() method and internal lock releases. 
Python-threading
Python
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