Sample code for the article on inner functions (#711)

* Sample code for the article on inner functions

* Final QA

---------

Co-authored-by: Bartosz Zaczyński <bartosz.zaczynski@gmail.com>

Author: lpozo

python-inner-functions/NYC_Wi-Fi_Hotspot_Locations.csv

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+# Python Inner Functions: What Are They Good For?
+
+This folder provides the code examples for the Real Python tutorial [Python Inner Functions: What Are They Good For?](https://realpython.com/inner-functions-what-are-they-good-for/).

python-inner-functions/README.md

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+def debug(func):
+    def _debug(*args, **kwargs):
+        result = func(*args, **kwargs)
+        print(f"{func.__name__}(args: {args}, kwargs: {kwargs}) -> {result}")
+        return result
+
+    return _debug
+
+
+@debug
+def add(a, b):
+    return a + b
+
+
+print(add(5, 6))

python-inner-functions/debugging.py

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+def factorial(number):
+    if not isinstance(number, int):
+        raise TypeError("number must be an integer")
+    if number < 0:
+        raise ValueError("number must be zero or positive")
+
+    def inner_factorial(number):
+        if number <= 1:
+            return 1
+        return number * inner_factorial(number - 1)
+
+    return inner_factorial(number)
+
+
+print(factorial(4))

python-inner-functions/factorial.py

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+import csv
+from collections import Counter
+from io import TextIOWrapper
+
+
+def process_hotspots(file: str | TextIOWrapper):
+    hotspots = []
+
+    if isinstance(file, str):
+        with open(file, "r") as csv_file:
+            for row in csv.DictReader(csv_file):
+                hotspots.append(row["Provider"])
+    else:
+        with file as csv_file:
+            for row in csv.DictReader(csv_file):
+                hotspots.append(row["Provider"])
+
+    provider, count = Counter(hotspots).most_common(1)[0]
+    print(
+        f"There are {len(hotspots)} Wi-Fi hotspots in NYC.\n"
+        f"{provider} has the most with {count}."
+    )
+
+
+if __name__ == "__main__":
+    process_hotspots("NYC_Wi-Fi_Hotspot_Locations.csv")

python-inner-functions/hotspots_v1.py

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+import csv
+from collections import Counter
+from io import TextIOWrapper
+
+
+def process_hotspots(file: str | TextIOWrapper):
+    hotspots = []
+
+    def extract_hotspots(csv_file):
+        for row in csv.DictReader(csv_file):
+            hotspots.append(row["Provider"])
+
+    if isinstance(file, str):
+        with open(file, "r") as csv_file:
+            extract_hotspots(csv_file)
+    else:
+        with file as csv_file:
+            extract_hotspots(csv_file)
+
+    provider, count = Counter(hotspots).most_common(1)[0]
+    print(
+        f"There are {len(hotspots)} Wi-Fi hotspots in NYC.\n"
+        f"{provider} has the most with {count}."
+    )

python-inner-functions/hotspots_v2.py

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+import csv
+from collections import Counter
+from io import TextIOWrapper
+
+
+def process_hotspots(file: str | TextIOWrapper):
+    if isinstance(file, str):
+        file = open(file, "r")
+
+    with file as csv_file:
+        hotspots = [row["Provider"] for row in csv.DictReader(csv_file)]
+
+    provider, count = Counter(hotspots).most_common(1)[0]
+    print(
+        f"There are {len(hotspots)} Wi-Fi hotspots in NYC.\n"
+        f"{provider} has the most with {count}."
+    )

python-inner-functions/hotspots_v3.py

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+def mean():
+    samples = []
+
+    def inner_mean(number):
+        samples.append(number)
+        return sum(samples) / len(samples)
+
+    return inner_mean
+
+
+sample_means = mean()
+
+print(sample_means(100))
+print(sample_means(105))
+print(sample_means(101))
+print(sample_means(98))

python-inner-functions/mean.py

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+def add_messages(func):
+    def _add_messages():
+        print("This is my first decorator")
+        func()
+        print("Bye!")
+
+    return _add_messages
+
+
+@add_messages
+def greet():
+    print("Hello, World!")
+
+
+greet()

python-inner-functions/message.py

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+def make_point(x, y):
+    def point():
+        print(f"Point({x}, {y})")
+
+    def get_x():
+        return x
+
+    def get_y():
+        return y
+
+    def set_x(value):
+        nonlocal x
+        x = value
+
+    def set_y(value):
+        nonlocal y
+        y = value
+
+    # Attach getters and setters
+    point.get_x = get_x
+    point.set_x = set_x
+    point.get_y = get_y
+    point.set_y = set_y
+    return point
+
+
+point = make_point(1, 2)
+print(point.get_x())
+print(point.get_y())
+point()
+
+point.set_x(42)
+point.set_y(7)
+point()