Log value of variable every second in Python

Question

I need to print the value of a variable every second or couple of seconds, while "at the same time" this variable is being modified. So I would be modifying this variable in my main function and I want something to print its value every second. Something like:

'''This is my main program'''

for i in range(very large number):

'''do something which modifies the value of 'var' '''

And somewhere else in the code:

'''Every second'''

print var

I took a look at this but I'm not sure if it's what I'm looking for, or how I should use it.

What I need is reaaaly simple, there are no other threads, and I don't care about syncing anything, or when in the main function the value is printed.

If you have no threads that paralelize the work (Modify var and print it's value) why you need to wait 1 second to print? — Mr. E, Nov 23 '15 at 13:45
You can't do such things without using multithreading or multiprocessing or asynchronous (like gevent or tornado) approaches. — Sergeev Andrew, Nov 23 '15 at 13:46

Kenly · Accepted Answer · 2015-11-23T14:14:05.380

3

You can use threading to print var each second.

try this example:

import threading

var = 5


def printit():
  global var
  threading.Timer(5.0, printit).start()
  print "Hello, World!", var

printit()

import time

for i in range(1000000):
    time.sleep(2)
    var = i

edited Nov 23 '15 at 14:14

answered Nov 23 '15 at 13:58

Kenly

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Both answers work, but this is the easiest. I just had to add a flag "done" so that when the other part finishes, this function stops. Otherwise it keeps running forever! – Chrischpo Nov 23 '15 at 14:23

GreenAsJade · Answer 2 · 2015-11-23T14:09:38.090

Basically, the question/answer you pointed to is what you need:

import threading import time

interesting = 0

class MonitorThread(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        global interesting
        while(1):
            print interesting
            time.sleep(1)

MonitorThread().start()

for interesting in range(2000000):
    time.sleep(1)

Log value of variable every second in Python

2 Answers2