printing dots using decorator while a function execute

Question

I am trying to write a decorator that will print dots in terminal while the function that calls the decorator executes.

import sys
from time import sleep


def call_counter(func):
    def helper(*args, **kwargs):
        for dot in xrange(0, 99):
            sys.stdout.write(".")
            sys.stdout.flush()
        return func(*args, **kwargs)
    helper.calls = 0
    helper.__name__= func.__name__
    return helper

@call_counter
def f():
    sleep(10)



if __name__ == "__main__":
    f()

this is what I have tried so far. But i am not getting expected result. for function taking time to execute I have used sleep of 10 seconds .

I thought that is what you expected to get? What *did* you expect? — mkrieger1, Jul 12 '20 at 15:47
continuous printing of dot while the `f` function exectues. in this case for 10 seconds — Chang Zhao, Jul 12 '20 at 15:52
But `helper` just writes a single dot before calling `func` and blocking while it is running. You need some sort of concurrency. — mkrieger1, Jul 12 '20 at 16:02
I believe this answers your question: https://stackoverflow.com/questions/7207309/python-how-can-i-run-python-functions-in-parallel — mkrieger1, Jul 12 '20 at 16:04
I have updated the decorator function , that prints dots, but now it straight away print 100 dots. if I use concurrency, then how should I register the calling function is complete ? do you get what I mean ? — Chang Zhao, Jul 12 '20 at 16:07

score 0 · Accepted Answer · answered Jul 12 '20 at 16:55

Whether you use decorators or not you cannot magically print the progress of a function without having this function willingly reporting its progress. Reporting the progress is usually done by passing a progress callback to the function. The function will at eg each iteration of an internal loop (provided it has some sort of loop) execute the user callback and pass a parameter denoting its current progress. something like

def long_func(data:list, progress):
tot = len(data)
for i,item in enumerate(data):
   #do something with item
   progress(i+1/tot)

in my long running function actually make call to a `subprocess.Popen` that takes long time not that there is something iterative that takes time. if it was an iterative I could have easily printed the progress and this post on SO wouldnt have existed. — Chang Zhao, Jul 18 '20 at 21:15

printing dots using decorator while a function execute

1 Answers1