[Python Atomic Counter] #python3 #concurrency #threadsafe #lock #atomic #counter

Python AtomicCounter.py

import threading


class AtomicCounter(object):
    """An atomic, thread-safe counter"""
    
    def __init__(self, initial=0):
        """Initialize a new atomic counter to given initial value"""
        self._value = initial
        self._lock = threading.Lock()
    
    def inc(self, num=1):
        """Atomically increment the counter by num and return the new value"""
        with self._lock:
            self._value += num
            return self._value
    
    def dec(self, num=1):
        """Atomically decrement the counter by num and return the new value"""
        with self._lock:
            self._value -= num
            return self._value
    
    @property
    def value(self):
        return self._value
      
counter = AtomicCounter()
counter.value  # 0
counter.inc()  # 1
counter.inc()  # 2
counter.dec()  # 1
counter.dec()  # 0
counter.dec()  # -1