Counting number of entries to a function in python

Question

I am new to python. It might seem little obvious but would like to know if there is any easier way in python to do this.

I am trying to count number entries to a function. Requirement is as below:

Every 5 sec a timer event is triggered through which callback (ev_5ms()) is inturn triggered
Wait until 20 secods and then clear the counter and start again

I am using the following code

counter = 0

"Callback"
def ev_5s():
if counter < 4:
    counter += 1
else
    counter = 0
    print('Send Message')

t = EventGenerator.TimerEventGenerator(1, ev_1s())
t.start()

Error Traceback:

Traceback (most recent call last):
File "C:/Users/i8479/Desktop/Python/HPP_SM.py", line 28, in <module>
t = EventGenerator.TimerEventGenerator(1, ev_1s())
File "C:/Users/i8479/Desktop/Python/HPP_SM.py", line 21, in ev_1s
if counter < 4:
UnboundLocalError: local variable 'counter' referenced before assignment

I am coding as I would do in c or cpp. How can I do this in python?

use `global counter` in the function to reference the counter variable. Anyway this is not a good practice — Netwave, Apr 09 '19 at 07:48

score 2 · Accepted Answer · answered Apr 09 '19 at 08:02

A pythonic way of doing this would be to have a decorator class, for example:

from functools import wraps
import time

class EventCounter(object):
  def __init__(self, reset_span):
    self.reset_span = reset_span
    self.running = False
    self.start_t = None
    self.counter = 0
  def __call__(self, f):
    @wraps(f)
    def wrapper(*args, **kwargs):
      if not self.running:
        self.start_t = time.time()
        self.counter += 1
        self.running = True
      elif (time.time() - self.start_t) > self.reset_span:
        self.start_t = time.time()
        self.counter = 0
      else:
        self.counter += 1
      print(f"Counter: {self.counter}")
      return f(*args, **kwargs)
    return wrapper


@EventCounter(2)
def foo():
  print("Foo")

Running:

for _ in range(5):
  foo()
  time.sleep(1)

results:

Counter: 1
Foo
Counter: 2
Foo
Counter: 0
Foo
Counter: 1
Foo
Counter: 0
Foo

Here you have the live example

score 0 · Answer 2 · answered Apr 09 '19 at 07:53

0

One of the solutions is global:

counter = 0

# Callback
def ev_5s():
    global counter
    if counter < 4:
        counter += 1
    else
        counter = 0
        print('Send Message')

t = EventGenerator.TimerEventGenerator(1, ev_1s())
t.start()

answered Apr 09 '19 at 07:53

Waket Zheng

5,065
2
17
30

score 0 · Answer 3 · answered Apr 09 '19 at 07:54

0

This means you are passing the variable counter into the function

Line to change

def ev_5s(counter):

Other line to change

t = EventGenerator.TimerEventGenerator(1, ev_1s(counter))

answered Apr 09 '19 at 07:54

GILO

2,444
21
47

Counting number of entries to a function in python

3 Answers3