"""Exercise 6.3.4 — Duck typing a method call

Chapter 6: Objects — Everyday Programming

Different timers each provide tick(), so one loop can advance them all.

This program contains exactly one bug. Solution: sol_6_3_4.py
"""

class Stopwatch:
    def __init__(self):
        self.seconds = 0

    def tick(self):
        self.seconds = self.seconds + 1

class Metronome:
    def __init__(self):
        self.beats = 0

    def tick(self):
        self.beats = self.beats + 1

def advance(devices):
    for device in devices:
        device.tick

watch = Stopwatch()
advance([watch])
print(watch.seconds)   # 1