Python Threading – In this tutorial, you will learn python threading example, multithreading in python with example, daemon thread python, non-daemon thread python with program examples.
THREADING
- Thread is a path of the execution within a process.
TASK BASED TYPES
- Single Threading
- Multithreading
DIFFERENCE BETWEEN SINGLE THREAD AND MULTIPLE THREADS
| S.N | SINGLE THREAD | MULTITHREADING |
| 1. | Performs single task | Performs multitasking. Doing more than one job at the same time |
| 2. | It consists of only one thread | It consists of several threads |
| 3. | It is used for experimental purpose | It is used for larger tasks. |
LIFE CYCLE OF THREADS
- Thread has five life cycles. It always lives in any of the states.
- New born state (New state)
- Runnable state
- Running state (execution state)
- Blocked state
- Dead state (End state).
BUILT-IN METHODS
1. start()
- This is runnable state (waiting for the execution)
- This is method is used to start the thread
- Return type : None
2. threading.currentThread().getName()
- This method is used to display the name of currently executing or running thread
- Return type : Str
Thread Creation
- Thread is created by using the built-in super class Thread Thread(name=<user-defined-name, target=<function-name>, )
- It is a built-in class which is used to create a new thread object
- It takes two or more arguments
- First argument is the name of the thread. It can be any name set by the user. It is optional argument
- Second argument is target which is used to call the user defined function
Required Module
I. EXAMPLE OF SINGLE THREAD
Tools used : VSC Editor
Platform OS : Windows 10
Language : Python 3
1. SOURCE CODE
from threading import *
# user defined function
def welcome():
print(“Hello World…”)
print(“——————————————“)
print(“\tSingle Thread”)
print(“——————————————“)
# creating object for single thread
t1=Thread(target=welcome, name=”Thread 1″)
# start the thread by calling start method
t1.start()
2. OUTPUT
Pictorial Representation
MULTITHREADING
- Process of executing more than one thread at the same time (Execution of multiple threads simultaneously)
- It is important to note that, we can’t predict which thread will run first.
- It is important to note that, the main or current thread can randomly start any thread from the list of threads.
II. EXAMPLE OF MULTITHREADING
(Asynchronous Processes)
Tools used : VSC Editor
Platform OS : Windows 10
Language : Python 3
1. SOURCE CODE
from threading import *
# user defined function 1
def m1():
for i in range(3):
print(“Good Morning…”)
# user defined function 2
def m2():
for i in range(3):
print(“Good Evening…”)
# user defined function 3
def m3():
for i in range(3):
print(“Good Night…”)
print(“——————————————“)
print(“\tMultithreading”)
print(“——————————————“)
# creating objects for multiple threads
t1=Thread(target=m1,name=”Morning”)
t2=Thread(target=m2,name=”Evening”)
t3=Thread(target=m3,name=”Night”)
# start the threads by calling start method
t1.start()
t2.start()
t3.start()
Pictorial Representation
2. OUTPUT
III. EXAMPLE OF MULTITHREADING
(Synchronous Processes using join() method)
Tools used : VSC Editor
Platform OS : Windows 10
Language : Python 3
Existing Issues
- By default, the threads are running parallel in multithreading
- In the execution of multithreading using asynchronous methods, the threads will be running in parallel. That’s why the output came differently in the previous example.
- So in order to execute threads one by one (sequential order) during the multithreading, the join method will be used.
1. SOURCE CODE
from threading import *
# user defined function 1
def m1():
for i in range(3):
print(“Good Morning…”)
# user defined function 2
def m2():
for i in range(3):
print(“Good Evening…”)
# user defined function 3
def m3():
for i in range(3):
print(“Good Night…”)
print(“——————————————“)
print(“\tMultithreading”)
print(“——————————————“)
# creating objects for multiple threads
t1=Thread(target=m1,name=”Morning”)
t2=Thread(target=m2,name=”Evening”)
t3=Thread(target=m3,name=”Night”)
# start thread 1
t1.start()
# wait until thread 1 is finished (main and sub threads t2, t3 should wait)
t1.join()
# start thread 2 after thread 1
t2.start()
# wait until thread 2 is finished (main and sub threads t1, t3 should wait)
t2.join()
# start thread 3 after thread 2
t3.start()
# wait until thread 3 is finished (main and sub threads t1, t2 should wait)
t3.join()
# end of the main thread
print(“End of the main thread…”)
2. OUTPUT
IV. DETECTION OF CURRENTLY EXECUTING THREAD
Tools used : VSC Editor
Platform OS : Windows 10
Language : Python 3
1. SOURCE CODE
from threading import *
import threading
# user defined function 1
def m1():
tname=threading.currentThread().getName()
print(“Current Thread\t: “,tname)
print(“Good Morning…”)
# user defined function 2
def m2():
tname=threading.currentThread().getName()
print(“Current Thread\t: “,tname)
print(“Good Evening…”)
# user defined function 3
def m3():
tname=threading.currentThread().getName()
print(“Current Thread\t: “,tname)
print(“Good Night…”)
# main thread
print(“——————————————-“)
print(“\tFinding Current Thread – Multithreading”)
print(“——————————————-“)
# creating objects for multiple threads
t1=Thread(target=m1,name=”Morning”)
t2=Thread(target=m2,name=”Evening”)
t3=Thread(target=m3,name=”Night”)
# start threads
t1.start()
t2.start()
t3.start()
# end of the main thread
print(“End of the main thread…”)
2. OUTPUT
GENERAL TYPES OF THREAD
- Like java, python supports two types of threads. They are
- Daemon thread
- Non daemon thread (User Thread)
1. Daemon Thread
- If a thread is running in background mode, then it is called as daemon thread
- It has low priority level than user thread
- This is created by adding the boolean value to the daemon argument of the Thread class.
2. Non Daemon Thread
- If a thread is running in foreground mode, then it is called as non daemon thread (user thread)
- It has high priority level than daemon thread
- This is created by the thread class.
DIFFERENCE BETWEEN DAEMON THREAD AND NON DAEMON THREAD
| S.N | DAEMON THREAD | NON DAEMON THREAD |
| 1. | It is always runs in background mode | It is always runs in foreground mode |
| 2. | Main program does not wait for daemon thread to finish its task | Here main program waits for user threads have to terminate |
| 3. | It has low priority | It has high priority |
| 4. | It is not used for important tasks. It is generally used for some background tasks which are not important | Any important task is done by the user thread. |
| 5. | It is created by the Python Virtual Machine (PVM) | It is created by the application or program. |
| 6. | If all the threads have finished their execution, the PVM will force the daemon threads to finish their execution. | PVM won’t force the user threads for termination. So it waits for user threads to terminate themselves. |
I. EXAMPLE OF DAEMON THREAD
Tools used : VSC Editor
Platform OS ;: Windows 10
Language : Python 3
1. SOURCE CODE
from threading import *
from time import sleep
# user defined function 1
def m1():
for i in range(3):
print(“Good Morning…”)
sleep(2)
# user defined function 2
def m2():
for i in range(3):
print(“Good Evening…”)
# user defined function 3
def m3():
for i in range(3):
print(“Good Night…”)
print(“————————————————“)
print(“\tDaemon Thread”)
print(“————————————————“)
# creating objects for multiple threads
# convert thread t1 to daemon thread by setting the boolean true to the daemon argument of thread class
t1=Thread(target=m1,name=”Morning”, daemon=True)
# non daemon threads
t2=Thread(target=m2,name=”Evening”)
t3=Thread(target=m3,name=”Night”)
# start the thread by calling start method
t1.start()
t2.start()
t3.start()
2. OUTPUT
NOTE
- In the above output screenshot, the daemon thread t1 Good Morning is still running in the background mode.
- Even Though all threads (including main thread) are terminated, the daemon thread is still alive and running in the background.
II. EXAMPLE OF NON DAEMON THREAD
Tools used : VSC Editor
Platform OS : Windows 10
Language : Python 3
1. SOURCE CODE
from threading import *
from time import sleep
# user defined function 1
def m1():
for i in range(3):
print(“Good Morning…”)
sleep(2)
# user defined function 2
def m2():
for i in range(3):
print(“Good Evening…”)
# user defined function 3
def m3():
for i in range(3):
print(“Good Night…”)
print(“——————————————-“)
print(“\tNon Daemon Thread(User Threads)”)
print(“——————————————-“)
# creating objects for multiple threads
# Non Daemon Threads
t1=Thread(target=m1,name=”Morning”)
t2=Thread(target=m2,name=”Evening”)
t3=Thread(target=m3,name=”Night”)
# start the threads by calling start method
t1.start()
t2.start()
t3.start()
2. OUTPUT
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