Added example solutions to several chapters. Feel free to create a pull request with your answers. Also for the chapters that have no solutions yet :)

CH_06_decorators/exercise_02/solution_00.py

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+# Extend the `track` function with min/max/average execution time and call 
+# count.
+import functools
+import random
+import time
+from datetime import datetime, timedelta
+
+
+def track(function=None, label=None):
+    # Trick to add an optional argument to our decorator
+    if label and not function:
+        return functools.partial(track, label=label)
+
+    execution_times = dict(
+        min=timedelta.max,
+        max=timedelta.min,
+        total=timedelta(),
+        count=0,
+    )
+
+    print(f'initializing {label}')
+
+    @functools.wraps(function)
+    def _track(*args, **kwargs):
+        print(f'calling {label}')
+
+        start = datetime.now()
+        result = function(*args, **kwargs)
+        end = datetime.now()
+
+        duration = end - start
+        execution_times['min'] = min(execution_times['min'], duration)
+        execution_times['max'] = max(execution_times['max'], duration)
+        execution_times['total'] += duration
+        execution_times['count'] += 1
+
+        print(f'called {label} in {duration}')
+        return result
+
+    def print_stats():
+        print(f'{label} stats:')
+        print(f'  min: {execution_times["min"]}')
+        print(f'  max: {execution_times["max"]}')
+        print(f'  total: {execution_times["total"]}')
+        print(f'  avg: {execution_times["total"] / execution_times["count"]}')
+
+    _track.print_stats = print_stats
+
+    return _track
+
+
+@track(label='random sleep')
+def random_sleep():
+    time.sleep(random.random())
+
+
+if __name__ == '__main__':
+    for i in range(10):
+        random_sleep()
+
+    random_sleep.print_stats()