Merge pull request #45 from realpython/understanding-async-python

Understanding async python

Author: dbader

understanding-asynchronous-programming/example_1.py

@@ -0,0 +1,37 @@
+import queue
+
+
+def task(name, work_queue):
+    if work_queue.empty():
+        print(f"Task {name} nothing to do")
+    else:
+        while not work_queue.empty():
+            count = work_queue.get()
+            total = 0
+            print(f"Task {name} running")
+            for x in range(count):
+                total += 1
+            print(f"Task {name} total: {total}")
+
+
+def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = queue.Queue()
+
+    # Put some 'work' in the queue
+    for work in [15, 10, 5, 2]:
+        work_queue.put(work)
+
+    # Create some synchronous tasks
+    tasks = [(task, "One", work_queue), (task, "Two", work_queue)]
+
+    # Run the tasks
+    for t, n, q in tasks:
+        t(n, q)
+
+
+if __name__ == "__main__":
+    main()

understanding-asynchronous-programming/example_2.py

@@ -0,0 +1,42 @@
+import queue
+
+
+def task(name, queue):
+    while not queue.empty():
+        count = queue.get()
+        total = 0
+        print(f"Task {name} running")
+        for x in range(count):
+            total += 1
+            yield
+        print(f"Task {name} total: {total}")
+
+
+def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = queue.Queue()
+
+    # Put some 'work' in the queue
+    for work in [15, 10, 5, 2]:
+        work_queue.put(work)
+
+    # Create some tasks
+    tasks = [task("One", work_queue), task("Two", work_queue)]
+
+    # Run the tasks
+    done = False
+    while not done:
+        for t in tasks:
+            try:
+                next(t)
+            except StopIteration:
+                tasks.remove(t)
+            if len(tasks) == 0:
+                done = True
+
+
+if __name__ == "__main__":
+    main()

understanding-asynchronous-programming/example_3.py

@@ -0,0 +1,45 @@
+import time
+import queue
+from lib.elapsed_time import ET
+
+
+def task(name, queue):
+    while not queue.empty():
+        delay = queue.get()
+        et = ET()
+        print(f"Task {name} running")
+        time.sleep(delay)
+        print(f"Task {name} total elapsed time: {et():.1f}")
+        yield
+
+
+def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = queue.Queue()
+
+    # Put some 'work' in the queue
+    for work in [15, 10, 5, 2]:
+        work_queue.put(work)
+
+    tasks = [task("One", work_queue), task("Two", work_queue)]
+
+    # Run the tasks
+    et = ET()
+    done = False
+    while not done:
+        for t in tasks:
+            try:
+                next(t)
+            except StopIteration:
+                tasks.remove(t)
+            if len(tasks) == 0:
+                done = True
+
+    print(f"\nTotal elapsed time: {et():.1f}")
+
+
+if __name__ == "__main__":
+    main()

understanding-asynchronous-programming/example_4.py

@@ -0,0 +1,35 @@
+import asyncio
+from lib.elapsed_time import ET
+
+
+async def task(name, work_queue):
+    while not work_queue.empty():
+        delay = await work_queue.get()
+        et = ET()
+        print(f"Task {name} running")
+        await asyncio.sleep(delay)
+        print(f"Task {name} total elapsed time: {et():.1f}")
+
+
+async def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = asyncio.Queue()
+
+    # Put some 'work' in the queue
+    for work in [15, 10, 5, 2]:
+        await work_queue.put(work)
+
+    # Run the tasks
+    et = ET()
+    await asyncio.gather(
+        asyncio.create_task(task("One", work_queue)),
+        asyncio.create_task(task("Two", work_queue)),
+    )
+    print(f"\nTotal elapsed time: {et():.1f}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

understanding-asynchronous-programming/example_5.py

@@ -0,0 +1,54 @@
+import queue
+import requests
+from lib.elapsed_time import ET
+
+
+def task(name, work_queue):
+    with requests.Session() as session:
+        while not work_queue.empty():
+            url = work_queue.get()
+            print(f"Task {name} getting URL: {url}")
+            et = ET()
+            session.get(url)
+            print(f"Task {name} total elapsed time: {et():.1f}")
+            yield
+
+
+def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = queue.Queue()
+
+    # Put some 'work' in the queue
+    for url in [
+        "http://google.com",
+        "http://yahoo.com",
+        "http://linkedin.com",
+        "http://apple.com",
+        "http://microsoft.com",
+        "http://facebook.com",
+        "http://twitter.com",
+    ]:
+        work_queue.put(url)
+
+    tasks = [task("One", work_queue), task("Two", work_queue)]
+
+    # Run the tasks
+    et = ET()
+    done = False
+    while not done:
+        for t in tasks:
+            try:
+                next(t)
+            except StopIteration:
+                tasks.remove(t)
+            if len(tasks) == 0:
+                done = True
+
+    print(f"\nTotal elapsed time: {et():.1f}")
+
+
+if __name__ == "__main__":
+    main()

understanding-asynchronous-programming/example_6.py

@@ -0,0 +1,46 @@
+import asyncio
+import aiohttp
+from lib.elapsed_time import ET
+
+
+async def task(name, work_queue):
+    async with aiohttp.ClientSession() as session:
+        while not work_queue.empty():
+            url = await work_queue.get()
+            print(f"Task {name} getting URL: {url}")
+            et = ET()
+            async with session.get(url) as response:
+                await response.text()
+            print(f"Task {name} total elapsed time: {et():.1f}")
+
+
+async def main():
+    """
+    This is the main entry point for the program
+    """
+    # Create the queue of 'work'
+    work_queue = asyncio.Queue()
+
+    # Put some 'work' in the queue
+    for url in [
+        "http://google.com",
+        "http://yahoo.com",
+        "http://linkedin.com",
+        "http://apple.com",
+        "http://microsoft.com",
+        "http://facebook.com",
+        "http://twitter.com",
+    ]:
+        await work_queue.put(url)
+
+    # Run the tasks
+    et = ET()
+    await asyncio.gather(
+        asyncio.create_task(task("One", work_queue)),
+        asyncio.create_task(task("Two", work_queue)),
+    )
+    print(f"\nTotal elapsed time: {et():.1f}")
+
+
+if __name__ == "__main__":
+    asyncio.run(main())

understanding-asynchronous-programming/lib/__init__.py

@@ -0,0 +1,13 @@
+"""
+This module contains a simple class to measure elapsed time
+"""
+
+import time
+
+
+class ET(object):
+    def __init__(self):
+        self.start_time = time.time()
+
+    def __call__(self):
+        return time.time() - self.start_time

understanding-asynchronous-programming/lib/elapsed_time.py

@@ -0,0 +1,10 @@
+aiohttp==3.5.4
+async-timeout==3.0.1
+attrs==19.1.0
+certifi==2019.3.9
+chardet==3.0.4
+idna==2.8
+multidict==4.5.2
+requests==2.21.0
+urllib3==1.24.2
+yarl==1.3.0