Merge pull request #639 from realpython/python-while-loop

Sample code for the article on `while` loops

Author: brendaweles

python-while-loop/README.md

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+# Python while Loops: Repeating Tasks Conditionally
+
+This folder provides the code examples for the Real Python tutorial [Python while Loops: Repeating Tasks Conditionally](https://realpython.com/python-while-loop/).

python-while-loop/api_calls.py

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+import random
+import time
+
+
+def is_api_available():
+    """Simulate API availability."""
+    time.sleep(1)
+    return random.choice([True, False, False, False])
+
+
+def make_api_call(request):
+    print(f"Making API call: {request}")
+    time.sleep(0.5)
+
+
+requests = iter(["Request 1", "Request 2", "Request 3"])
+request = next(requests)
+
+while True:
+    if not is_api_available():
+        print("API not available. Retrying in 1 sec...")
+        continue
+    make_api_call(request)
+    try:
+        request = next(requests)
+    except StopIteration:
+        break
+
+print("All requests processed.")

python-while-loop/check_file.py

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+import time
+from pathlib import Path
+
+filename = Path("hello.txt")
+
+print(f"Waiting for {filename.name} to be created...")
+
+while not filename.exists():
+    print("File not found. Retrying in 1 second...")
+    time.sleep(1)
+
+print(f"{filename} found! Proceeding with processing.")
+with open(filename, mode="r") as file:
+    print("File contents:")
+    print(file.read())

python-while-loop/connection.py

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+import random
+import time
+
+MAX_RETRIES = 5
+attempts = 0
+
+while attempts < MAX_RETRIES:
+    attempts += 1
+    print(f"Attempt {attempts}: Connecting to the server...")
+    # Simulating a connection scenario
+    time.sleep(0.5)
+    if random.choice([False, False, False, True]):
+        print("Connection successful!")
+        break
+
+    print("Connection failed. Retrying...")
+else:
+    print("All attempts failed. Unable to connect.")

python-while-loop/infinite.py

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+# number = 5
+# while number != 0:
+#     print(number)
+#     number -= 2
+
+
+number = 5
+while number > 0:
+    print(number)
+    number -= 2
+
+
+number = 5
+while number != 0:
+    if number <= 0:
+        break
+    print(number)
+    number -= 2

python-while-loop/logfile.py

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+import time
+
+with open("file.log", mode="r") as file:
+    file.seek(0, 2)
+
+    while True:
+        line = file.readline()
+        if line:
+            line_content = line.strip()
+            if line_content == "END":
+                print("File processing done.")
+                break
+            print(f"Processing line content: {line_content}")
+        else:
+            time.sleep(1)
+            print("No new content. Retrying in 1 second...")

python-while-loop/password.py

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+MAX_ATTEMPTS = 3
+
+correct_password = "secret123"
+attempts = 0
+
+
+while True:
+    password = input("Password: ").strip()
+
+    attempts += 1
+    if attempts >= MAX_ATTEMPTS:
+        print("Too many failed attempts.")
+        break
+
+    if password == correct_password:
+        print("Login successful! Welcome!")
+        break
+    else:
+        print(f"Incorrect password. {MAX_ATTEMPTS - attempts} attempts left.")

python-while-loop/remove.py

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+colors = ["red", "blue", "yellow", "green"]
+
+while colors:
+    color = colors.pop(-1)
+    print(f"Processing color: {color}")

python-while-loop/temperature.py

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+import random
+import time
+
+
+def read_temperature():
+    time.sleep(1)
+    return random.uniform(20.0, 30.0)
+
+
+while True:
+    temperature = read_temperature()
+    print(f"Temperature: {temperature:.2f}°C")
+
+    if temperature >= 25:
+        print("Required temperature reached! Stopping monitoring.")
+        break

python-while-loop/user_input.py

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+line = input("Type some text: ")
+
+while line != "stop":
+    print(line)
+    line = input("Type some text: ")
+
+
+while (line := input("Type some text: ")) != "stop":
+    print(line)