Merge pull request #392 from realpython/python-raise-exception

Sample code for the article on raising exceptions

Author: KateFinegan

python-raise-exception/README.md

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+# Python's raise: Effectively Raising Exceptions in Your Code
+
+This folder provides the code examples for the Real Python tutorial [Python's raise: Effectively Raising Exceptions in Your Code](https://realpython.com/python-raise-exception/).

python-raise-exception/api.py

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+import requests
+
+
+class APIError(Exception):
+    pass
+
+
+def call_external_api(url):
+    try:
+        response = requests.get(url)
+        response.raise_for_status()
+        data = response.json()
+    except requests.RequestException as error:
+        raise APIError(f"{error}") from None
+    return data
+
+
+print(call_external_api("https://api.github.com/events"))

python-raise-exception/bare.py

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+import logging
+
+try:
+    result = 42 / 0
+except Exception as error:
+    logging.error(error)
+    raise error

python-raise-exception/devide.py

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+def divide(x, y):
+    for arg in (x, y):
+        if not isinstance(arg, int | float):
+            raise TypeError(f"number expected, got {type(arg).__name__}")
+    if y == 0:
+        raise ValueError("denominator can't be zero")
+    return x / y
+
+
+try:
+    divide(42, 0)
+except Exception as error:
+    raise ValueError("invalid argument") from error

python-raise-exception/devide2.py

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+class MathLibraryError(Exception):
+    pass
+
+
+def divide(a, b):
+    try:
+        return a / b
+    except ZeroDivisionError as ex:
+        raise MathLibraryError(ex)

python-raise-exception/grade.py

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+class GradeValueError(Exception):
+    pass
+
+
+def calculate_average_grade(grades):
+    total = 0
+    count = 0
+    for grade in grades:
+        if grade < 0 or grade > 100:
+            raise GradeValueError(
+                "grade values must be between 0 and 100 inclusive"
+            )
+        total += grade
+        count += 1
+    return round(total / count, 2)

python-raise-exception/group.py

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+try:
+    raise ExceptionGroup(
+        "several errors",
+        [
+            ValueError("invalid value"),
+            TypeError("invalid type"),
+            KeyError("missing key"),
+        ],
+    )
+except* ValueError:
+    print("Handling ValueError")
+except* TypeError:
+    print("Handling TypeError")
+except* KeyError:
+    print("Handling KeyError")
+
+
+try:
+    raise ExceptionGroup(
+        "several errors",
+        [
+            ValueError("invalid value"),
+            TypeError("invalid type"),
+            KeyError("missing key"),
+        ],
+    )
+except ExceptionGroup:
+    print("Got an exception group!")

python-raise-exception/prime.py

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+from math import sqrt
+
+
+def is_prime(number):
+    if not isinstance(number, int):
+        raise TypeError(
+            f"integer number expected, got {type(number).__name__}"
+        )
+    if number < 2:
+        raise ValueError(f"integer above 1 expected, got {number}")
+    for candidate in range(2, int(sqrt(number)) + 1):
+        if number % candidate == 0:
+            return False
+    return True

python-raise-exception/square.py

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+def squared(numbers):
+    if not isinstance(numbers, list | tuple):
+        raise TypeError(
+            f"list or tuple expected, got '{type(numbers).__name__}'"
+        )
+    return [number**2 for number in numbers]