Merge pull request #387 from realpython/python-callable-instances

Sample code for the callable instances article

Author: KateFinegan

python-callable-instances/README.md

@@ -0,0 +1,3 @@
+# Python's .__call__() Method: Creating Callable Instances
+
+This folder provides the code examples for the Real Python tutorial [Python's .__call__() Method: Creating Callable Instances](https://realpython.com/python-callable-instances/).

python-callable-instances/counter.py

@@ -0,0 +1,9 @@
+class Counter:
+    def __init__(self):
+        self.count = 0
+
+    def increment(self):
+        self.count += 1
+
+    def __call__(self):
+        self.increment()

python-callable-instances/cumulative_average.py

@@ -0,0 +1,17 @@
+def cumulative_average():
+    data = []
+
+    def average(new_value):
+        data.append(new_value)
+        return sum(data) / len(data)
+
+    return average
+
+
+class CumulativeAverager:
+    def __init__(self):
+        self.data = []
+
+    def __call__(self, new_value):
+        self.data.append(new_value)
+        return sum(self.data) / len(self.data)

python-callable-instances/factorial.py

@@ -0,0 +1,8 @@
+class Factorial:
+    def __init__(self):
+        self.cache = {0: 1, 1: 1}
+
+    def __call__(self, number):
+        if number not in self.cache:
+            self.cache[number] = number * self(number - 1)
+        return self.cache[number]

python-callable-instances/gui.py

@@ -0,0 +1,10 @@
+class MainWindow:
+    def show(self):
+        print("Showing the app's main window...")
+
+    def __call__(self):
+        self.show()
+
+
+window = MainWindow()
+window.show()  # Or just window()

python-callable-instances/init_vs_call.py

@@ -0,0 +1,8 @@
+class Demo:
+    def __init__(self, attr):
+        print(f"Initialize an instance of {self.__class__.__name__}")
+        self.attr = attr
+        print(f"{self.attr=}")
+
+    def __call__(self, arg):
+        print(f"Call an instance of {self.__class__.__name__} with {arg}")

python-callable-instances/logger.py

@@ -0,0 +1,7 @@
+class Logger:
+    def __init__(self, filename):
+        self.filename = filename
+
+    def __call__(self, message):
+        with open(self.filename, mode="a", encoding="utf-8") as log_file:
+            log_file.write(message + "\n")

python-callable-instances/power.py

@@ -0,0 +1,6 @@
+class PowerFactory:
+    def __init__(self, exponent):
+        self.exponent = exponent
+
+    def __call__(self, base):
+        return base**self.exponent

python-callable-instances/serializing.py

@@ -0,0 +1,21 @@
+import json
+
+import yaml
+
+
+class JsonSerializer:
+    def __call__(self, data):
+        return json.dumps(data, indent=4)
+
+
+class YamlSerializer:
+    def __call__(self, data):
+        return yaml.dump(data)
+
+
+class DataSerializer:
+    def __init__(self, serializer_strategy):
+        self.serializer_strategy = serializer_strategy
+
+    def serialize(self, data):
+        return self.serializer_strategy(data)

python-callable-instances/timing.py

@@ -0,0 +1,37 @@
+import time
+
+# class ExecutionTimer:
+#     def __init__(self, func):
+#         self.func = func
+
+#     def __call__(self, *args, **kwargs):
+#         start = time.perf_counter()
+#         result = self.func(*args, **kwargs)
+#         end = time.perf_counter()
+#         print(f"{self.func.__name__}() took {(end - start) * 1000:.4f} ms")
+#         return result
+
+
+class ExecutionTimer:
+    def __init__(self, repetitions=1):
+        self.repetitions = repetitions
+
+
+def __call__(self, func):
+    def timer(*args, **kwargs):
+        result = None
+        total_time = 0
+        print(f"Running {func.__name__}() {self.repetitions} times")
+        for _ in range(self.repetitions):
+            start = time.time()
+            result = func(*args, **kwargs)
+            end = time.time()
+            total_time += end - start
+        average_time = total_time / self.repetitions
+        print(
+            f"{func.__name__}() takes "
+            f"{average_time * 1000:.4f} ms on average"
+        )
+        return result
+
+    return timer