Reading the results from an infinite loop using threads in python

Question

I am currently working with python v.2.7 on windows 8.

My programme is using threads. The threads execute a method named as getData() for infinite time that does the following:

makes the current thread to sleep for some time
calls the compareValues()
retrieve the information from the compareValues() and adds them to a list called myList

The compareValues() does the following:

generates a random number
checks if it is less than 5 or if it is greater than or equal to 5 and yields the result along with the current thread's name

I save the results of these threads to a list named as myList and then finally print this myList.

Problem: As the getData() is looping for infinite time. How can I access the myList for retrieving the results? What would be a good approach in this case. If you remove the while True: then the programm works fine.

Code:

import time
from random import randrange
import threading

myList = []
def getData(i):
   while True:
        print "Sleep for %d"%i
        time.sleep(i)
        data = compareValues()
        for d in list(data):
            myList.append(d)

def compareValues():
        number = randrange(10)
        name = threading.current_thread().name
        if number >= 5:
             yield "%s: Greater than or equal to 5: %d  "%(name, number)
        else:
             yield "%s: Less than 5: %d  "%(name, number)

threadList = []
wait = randrange(10)+1
t = threading.Thread(name = 'First-Thread', target = getData, args=(wait,))
threadList.append(t)
t.start()
wait = randrange(3)+1
t = threading.Thread(name = 'Second-Thread', target = getData, args=(wait,))
threadList.append(t)
t.start()
for t in threadList:
    t.join()
print "The final list"
print myList

Thank you for your time.

This is an example of my real world problem. In my real world problem I have to read some different values from a server and update my old values respectively after every 5 seconds or so. So, I want to read values from the server infinitely. I just tried to convert my real world problem to this dummy problem. :) — ρss
– ρss, Commented Mar 10, 2014 at 8:43

Javier · Accepted Answer · 2014-03-10 20:49:52Z

1

I see a couple of inconsistencies that may help to make the code look a little bit more clear. For instance:

compareValues() should return 'The result in string Format......' and not yield. Am I right? Because this function is going to evaluate only one value at a time.

getData() should look like:

def getData(i):
    while True:
        print "Sleep for %d"%i
        time.sleep(i)
        myList.append(compareValues())

Exactly for the same reason as I said in the previous point.

P.S.: I don't know why the code is not formatting properly. Sorry... :-(

I hope it helps!

answered Mar 10, 2014 at 20:49

Javier

1,09714 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

ρss Over a year ago

Yes, your suggestions provided some hints that assisted me to solve my problem by modifying my code.

Javier Over a year ago

Wonderful! I'm happy about that.

Collectives™ on Stack Overflow

Reading the results from an infinite loop using threads in python

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related