Sample code for the article on best practices

Author: lpozo

python-best-practices/README.md

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+# Python Best Practices: From Messy to Pythonic Code
+
+This folder provides the code examples for the Real Python tutorial [Python Best Practices: From Messy to Pythonic Code](https://realpython.com/python-best-practice/).

python-best-practices/classes.py

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+# Avoid this:
+# class Article:
+#     def __init__(self, title, body, tags, db):
+#         self.title = title
+#         self.body = body
+#         self.tags = tags or []
+#         self.db = db
+#         self.slug = None
+#         self.published = False
+
+#     def publish(self):
+#         if self.slug is None:
+#             self.slug = "-".join(self.title.lower().split())
+
+#         self.db.save_article(
+#             title=self.title,
+#             body=self.body,
+#             tags=self.tags,
+#             slug=self.slug,
+#         )
+
+#         self.published = True
+
+
+# Favor this:
+from dataclasses import dataclass, field
+from datetime import datetime
+
+
+@dataclass
+class Article:
+    title: str
+    body: str
+    tags: list[str] = field(default_factory=list)
+    created_at: datetime = field(default_factory=datetime.utcnow)
+    published_at: datetime | None = None
+
+    @property
+    def is_published(self) -> bool:
+        return self.published_at is not None
+
+    @property
+    def slug(self) -> str:
+        return "-".join(self.title.lower().split())
+
+    def __str__(self) -> str:
+        status = "published" if self.is_published else "draft"
+        return f"{self.title} [{status}]"
+
+
+class Publisher:
+    def __init__(self, db):
+        self._db = db
+
+    def publish(self, article: Article) -> None:
+        if article.is_published:
+            return
+        article.published_at = datetime.utcnow()
+        self._db.save(article)

python-best-practices/code_style.py

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+# Avoid this:
+# def addNum(a,b):return a+  b
+
+
+# Favor this:
+def add_numbers(a, b):
+    return a + b

python-best-practices/comments.py

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+# Avoid this:
+# def find_index(sorted_items, target):
+#     # Set left index
+#     left = 0
+#     # Set right index
+#     right = len(sorted_items) - 1
+#     # Loop while left is less than right
+#     while left <= right:
+#         # Compute middle
+#         mid = (left + right) // 2
+#         # Check if equal
+#         if sorted_items[mid] == target:
+#             # Return mid
+#             return mid
+#         # Check if less than target
+#         elif sorted_items[mid] < target:
+#             # Move left up
+#             left = mid + 1
+#         else:
+#             # Move right down
+#             right = mid - 1
+#     # Return -1 if not found
+#     return -1
+
+
+# Favor this:
+def find_index(sorted_items, target):
+    """Return the index of target in sorted_items, or -1 if not found."""
+    left = 0
+    right = len(sorted_items) - 1
+
+    while left <= right:
+        mid = (left + right) // 2
+        value = sorted_items[mid]
+
+        if value == target:
+            return mid
+
+        # If target is larger, you can safely ignore the left half
+        if value < target:
+            left = mid + 1
+        # Otherwise, target must be in the left half (if present)
+        else:
+            right = mid - 1
+
+    return -1

python-best-practices/comprehensions.py

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+# Avoid this:
+# cubes = []
+# for number in range(10):
+#     cubes.append(number**3)
+
+# Favor this:
+cubes = [number**3 for number in range(10)]
+cubes

python-best-practices/concurrency.py

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+# Avoid this:
+# import asyncio
+
+# import requests
+
+# async def main():
+#     await asyncio.gather(
+#         fetch_status("https://example.com"),
+#         fetch_status("https://python.org"),
+#     )
+
+# async def fetch_status(url):
+#     response = requests.get(url)  # Blocking I/O task
+#     return response.status_code
+
+# asyncio.run(main())
+
+
+# Favor this:
+import asyncio
+
+import aiohttp
+
+
+async def main():
+    async with aiohttp.ClientSession() as session:
+        statuses = await asyncio.gather(
+            fetch_status(session, "https://example.com"),
+            fetch_status(session, "https://realpython.com"),
+        )
+    print(statuses)
+
+
+async def fetch_status(session, url):
+    async with session.get(url) as response:  # Non-blocking I/O task
+        return response.status
+
+
+asyncio.run(main())

python-best-practices/conditionals.py

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+# Avoid this:
+# def shipping_cost(country, items):
+#     if country is not None:
+#         if country == "US":
+#             if len(items) > 0:  # Non-empty cart?
+#                 if len(items) > 10:  # Free shipping?
+#                     return 0
+#                 else:
+#                     return 5
+#             else:
+#                 return 0
+#         elif country == "CA":
+#             if len(items) > 0:  # Non-empty cart?
+#                 return 10
+#             else:
+#                 return 0
+#         else:
+#             # Other countries
+#             if len(items) > 0:  # Non-empty cart?
+#                 return 20
+#             else:
+#                 return 0
+#     else:
+#         raise ValueError("invalid country")
+
+
+# Favor this:
+def shipping_cost(country, items):
+    if country is None:
+        raise ValueError("invalid country")
+
+    if not items:  # Empty cart?
+        return 0
+
+    if country == "US":
+        return 0 if len(items) > 10 else 5
+
+    if country == "CA":
+        return 10
+
+    return 20  # Other countries

python-best-practices/docstrings.py

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+# Avoid this:
+# def add(a, b):
+#     """Return the sum of a and b."""
+#     return a + b
+
+
+# Favor this:
+def add(a, b):
+    """Sum two numbers.
+
+    Args:
+        a (int or float): The first number.
+        b (int or float): The second number.
+
+    Returns:
+        int or float: The sum of the two numbers.
+    """
+    return a + b

python-best-practices/exceptions.py

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+# Avoid this:
+# import json
+
+
+# def load_config(path):
+#     try:
+#         with open(path, encoding="utf-8") as config:
+#             data = json.load(config)
+#     except Exception:
+#         # If something went wrong, return an empty config
+#         return {}
+#     return data
+
+
+# def main():
+#     try:
+#         config = load_config("settings.json")
+#     except Exception:
+#         print("Sorry, something went wrong.")
+#     # Do something with config...
+
+
+# Favor this:
+import json
+import logging
+
+log = logging.getLogger(__name__)
+
+
+class ConfigError(Exception):
+    """Raised when issues occur with config file."""
+
+
+def load_config(path):
+    try:
+        with open(path, encoding="utf-8") as config:
+            data = json.load(config)
+    except FileNotFoundError as error:
+        raise ConfigError(f"Config file not found: {path}") from error
+    except json.JSONDecodeError as error:
+        raise ConfigError(f"Invalid JSON: {path}") from error
+    return data
+
+
+def main():
+    try:
+        config = load_config("settings.json")
+        print("Config:", config)
+    except ConfigError as error:
+        log.error("Error loading the config: %s", error)
+        print("Sorry, something went wrong while loading the settings.")
+    # Do something with config...

python-best-practices/functions.py

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+# Avoid this:
+# import csv
+
+# def process_users(users, min_age, filename, send_email):
+#     adults = []
+#     for user in users:
+#         if user["age"] >= min_age:
+#             adults.append(user)
+
+#     with open(filename, mode="w", newline="", encoding="utf-8") as csv_file:
+#         writer = csv.writer(csv_file)
+#         writer.writerow(["name", "age"])
+#         for user in adults:
+#             writer.writerow([user["name"], user["age"]])
+
+#     if send_email:
+#         # Emailing logic here...
+
+#     return adults, filename
+
+# Favor this:
+import csv
+
+
+def filter_adult_users(users, *, min_age=18):
+    """Return users whose age is at least min_age."""
+    return [user for user in users if user["age"] >= min_age]
+
+
+def save_users_csv(users, filename):
+    """Save users to a CSV file."""
+    with open(filename, mode="w", newline="", encoding="utf-8") as csv_file:
+        writer = csv.writer(csv_file)
+        writer.writerow(["name", "age"])
+        for user in users:
+            writer.writerow([user["name"], user["age"]])
+
+
+def send_users_report(filename):
+    """Send the report."""
+    # Emailing logic here...