Merge pull request #370 from realpython/python-del-statement

Sample code for the article on `del`

Author: KateFinegan

python-del-statement/README.md

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+# Python's del: Remove References From Scopes and Containers
+
+This folder provides the code examples for the Real Python tutorial [Python's del: Remove References From Scopes and Containers](https://realpython.com/python-del-statement/).

python-del-statement/custom_dict.py

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+class Dict(dict):
+    def __delitem__(self, key) -> None:
+        print(f"Running .__delitem__() to delete {(key, self[key])}")
+        super().__delitem__(key)

python-del-statement/custom_list.py

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+class List(list):
+    def __delitem__(self, index):
+        print(f"Running .__delitem__() to delete {self[index]}")
+        super().__delitem__(index)

python-del-statement/factorial.py

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+class Factorial:
+    def __init__(self, number):
+        self._number = number
+        self._cache = {0: 1, 1: 1}
+        self._factorial = self._calculate_factorial(number)
+        del self._cache
+
+    def _calculate_factorial(self, number):
+        if number in self._cache:
+            return self._cache[number]
+        current_factorial = number * self._calculate_factorial(number - 1)
+        self._cache[number] = current_factorial
+        return current_factorial
+
+    @property
+    def number(self):
+        return self._number
+
+    @property
+    def factorial(self):
+        return self._factorial
+
+    def __str__(self) -> str:
+        return f"{self._number}! = {self._factorial}"
+
+    def __repr__(self):
+        return f"{type(self).__name__}({self._number})"

python-del-statement/non_deleteable.py

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+class NonDeleteable:
+    def __init__(self, value):
+        self.value = value
+
+    def __delattr__(self, name):
+        raise AttributeError(
+            f"{type(self).__name__} object doesn't support attribute deletion"
+        )

python-del-statement/person.py

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+class Person:
+    def __init__(self, name):
+        self.name = name
+
+    @property
+    def name(self):
+        return self._name
+
+    @name.setter
+    def name(self, value):
+        self._name = str(value).upper()
+
+    @name.deleter
+    def name(self):
+        raise AttributeError("can't delete attribute 'name'")

python-del-statement/sample.py

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+class SampleClass:
+    class_attribute = 0
+
+    def __init__(self, arg):
+        self.instance_attribute = arg
+
+    def method(self):
+        print(self.instance_attribute)