Merge pull request #360 from realpython/python-iterators-iterables

Sample code for the iterators and iterables article

Author: KateFinegan

python-iterators-iterables/README.md

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+# Iterators and Iterables in Python: Run Efficient Iterations
+
+This folder provides the code examples for the Real Python tutorial [Iterators and Iterables in Python: Run Efficient Iterations](https://realpython.com/python-iterators-iterables/).

python-iterators-iterables/async_iter.py

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+import asyncio
+from random import randint
+
+
+class AsyncIterable:
+    def __init__(self, stop):
+        self.stop = stop
+        self.index = 0
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        if self.index >= self.stop:
+            raise StopAsyncIteration
+        await asyncio.sleep(value := randint(1, 3))
+        self.index += 1
+        return value
+
+
+async def main():
+    async for num in AsyncIterable(4):
+        print(num)
+
+
+asyncio.run(main())

python-iterators-iterables/fib_gen.py

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+# def fibonacci_generator(stop=10):
+#     current_fib, next_fib = 0, 1
+#     for _ in range(0, stop):
+#         fib_number = current_fib
+#         current_fib, next_fib = next_fib, current_fib + next_fib
+#         yield fib_number
+
+
+def fibonacci_generator(stop=10):
+    current_fib, next_fib = 0, 1
+    index = 0
+    while True:
+        if index == stop:
+            return
+        index += 1
+        fib_number = current_fib
+        current_fib, next_fib = next_fib, current_fib + next_fib
+        yield fib_number

python-iterators-iterables/fib_iter.py

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+class FibonacciIterator:
+    def __init__(self, stop=10):
+        self._stop = stop
+        self._index = 0
+        self._current = 0
+        self._next = 1
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self._index < self._stop:
+            self._index += 1
+            fib_number = self._current
+            self._current, self._next = (
+                self._next,
+                self._current + self._next,
+            )
+            return fib_number
+        else:
+            raise StopIteration

python-iterators-iterables/inf_fib.py

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+class FibonacciInfIterator:
+    def __init__(self):
+        self._index = 0
+        self._current = 0
+        self._next = 1
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        self._index += 1
+        fib_number = self._current
+        self._current, self._next = self._next, self._current + self._next
+        return fib_number

python-iterators-iterables/inf_int.py

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+class InfIntegers:
+    def __init__(self):
+        self._number = 0
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        number = self._number
+        self._number += 1
+        return number

python-iterators-iterables/pipeline.py

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+def to_square(numbers):
+    return (number**2 for number in numbers)
+
+
+def to_cube(numbers):
+    return (number**3 for number in numbers)
+
+
+def to_even(numbers):
+    return (number for number in numbers if number % 2 == 0)
+
+
+def to_odd(numbers):
+    return (number for number in numbers if number % 2 != 0)
+
+
+def to_string(numbers):
+    return (str(number) for number in numbers)
+
+
+print(list(to_string(to_square(to_even(range(20))))))
+print(list(to_string(to_cube(to_odd(range(20))))))

python-iterators-iterables/resettable_iter.py

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+class ResettableRange:
+    def __init__(self, start=0, end=None, step=1, *, resettable=False):
+        if end is None:
+            end, start = start, 0
+        self._start = start
+        self._end = end
+        self._step = step
+        self._resettable = resettable
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self._start >= self._end:
+            if self._resettable:
+                self._start = 0
+            raise StopIteration
+        value = self._start
+        self._start += self._step
+        return value

python-iterators-iterables/reusable_range.py

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+class ReusableRange:
+    def __init__(self, start=0, stop=None, step=1):
+        if stop is None:
+            stop, start = start, 0
+        self._range = range(start, stop, step)
+        self._iter = iter(self._range)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        try:
+            return next(self._iter)
+        except StopIteration:
+            self._iter = iter(self._range)
+            raise

python-iterators-iterables/sequence_iter.py

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+class SequenceIterator:
+    def __init__(self, sequence):
+        self._sequence = sequence
+        self._index = 0
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if self._index < len(self._sequence):
+            item = self._sequence[self._index]
+            self._index += 1
+            return item
+        else:
+            raise StopIteration
+
+
+class Iterable:
+    def __init__(self, sequence):
+        self.sequence = sequence
+
+    def __iter__(self):
+        return SequenceIterator(self.sequence)