Update materials after final QA

Author: martin-martin

python-deque/custom_queue.py

@@ -12,6 +12,7 @@ def dequeue(self):
         try:
             return self._items.popleft()
         except IndexError:
+            # Break exception chain to hide implementation details
             raise IndexError("dequeue from an empty queue") from None
 
     def __len__(self):
@@ -20,11 +21,23 @@ def __len__(self):
     def __contains__(self, item):
         return item in self._items
 
-    def __str__(self):
-        return f"Queue({list(self._items)})"
-
     def __iter__(self):
         yield from self._items
 
     def __reversed__(self):
         yield from reversed(self._items)
+
+    def __repr__(self):
+        return f"Queue({list(self._items)})"
+
+
+if __name__ == "__main__":
+    queue = Queue()
+    print("Enqueueing items with '.enqueue()'...")
+    queue.enqueue(1)
+    queue.enqueue(2)
+    queue.enqueue(3)
+    print(queue)
+    print("Dequeueing one item with '.dequeue()'...")
+    print(queue.dequeue())
+    print(queue)

python-deque/page.py

@@ -0,0 +1,18 @@
+from collections import deque
+
+page_history = deque(maxlen=3)
+
+urls = ("https://google.com", "https://yahoo.com", "https://www.bing.com")
+
+for url in urls:
+    page_history.appendleft(url)
+
+print(page_history)
+
+page_history.appendleft("https://youtube.com")
+
+print(page_history)
+
+page_history.appendleft("https://facebook.com")
+
+print(page_history)

python-deque/page_history.py

@@ -7,7 +7,7 @@
 logging.basicConfig(level=logging.INFO, format="%(message)s")
 
 
-def wait_seconds(mins, maxs):
+def _wait_seconds(mins, maxs):
     time.sleep(mins + random.random() * (maxs - mins))
 
 
@@ -19,7 +19,7 @@ def produce(queue, size):
             logging.info("Produced: %d -> %s", value, str(queue))
         else:
             logging.info("Queue is saturated")
-        wait_seconds(0.1, 0.5)
+        _wait_seconds(0.1, 0.5)
 
 
 def consume(queue):
@@ -30,7 +30,7 @@ def consume(queue):
             logging.info("Queue is empty")
         else:
             logging.info("Consumed: %d -> %s", value, str(queue))
-        wait_seconds(0.2, 0.7)
+        _wait_seconds(0.2, 0.7)
 
 
 logging.info("Starting Threads...\n")

python-deque/producer_consumer.py

@@ -4,6 +4,10 @@
 def tail(filename, lines=10):
     try:
         with open(filename) as file:
-            return deque(file, lines)
+            return deque(file, maxlen=lines)
     except OSError as error:
         print(f'Opening file "{filename}" failed with error: {error}')
+
+
+if __name__ == "__main__":
+    print(tail("./README.md"))

python-deque/rotate.py

@@ -2,6 +2,7 @@
 from time import perf_counter
 
 TIMES = 10_000
+NANOSECONDS_PER_SECOND = 1e9
 a_list = []
 a_deque = deque()
 
@@ -11,7 +12,8 @@ def average_time(func, times):
     for i in range(times):
         start = perf_counter()
         func(i)
-        total += (perf_counter() - start) * 1e9
+        # Convert to ns to improve readability
+        total += (perf_counter() - start) * NANOSECONDS_PER_SECOND
     return total / times
 
 

python-deque/tail.py

@@ -1,7 +1,8 @@
 from collections import deque
 from time import perf_counter
 
-TIMES = 10000
+TIMES = 10_000
+NANOSECONDS_PER_SECOND = 1e9
 a_list = [1] * TIMES
 a_deque = deque(a_list)
 
@@ -11,13 +12,14 @@ def average_time(func, times):
     for _ in range(times):
         start = perf_counter()
         func()
-        total += (perf_counter() - start) * 1e9
+        # Convert to ns to improve readability
+        total += (perf_counter() - start) * NANOSECONDS_PER_SECOND
     return total / times
 
 
 list_time = average_time(lambda: a_list.pop(0), TIMES)
 deque_time = average_time(lambda: a_deque.popleft(), TIMES)
 gain = list_time / deque_time
 
-print(f"list.pop()      {list_time:.6} ns")
+print(f"list.pop(0)     {list_time:.6} ns")
 print(f"deque.popleft() {deque_time:.6} ns  ({gain:.6}x faster)")

python-deque/threads.py

@@ -2,6 +2,7 @@
 from time import perf_counter
 
 TIMES = 10_000
+MICROSECONDS_PER_SECOND = 1e6
 a_list = [1] * TIMES
 a_deque = deque(a_list)
 
@@ -11,7 +12,8 @@ def average_time(func, times):
     for _ in range(times):
         start = perf_counter()
         func()
-        total += (perf_counter() - start) * 1e6
+        # Convert to μs to improve readability
+        total += (perf_counter() - start) * MICROSECONDS_PER_SECOND
     return total / times