refactor: Simplify expo, decay, and fibo wait generators

CHANGELOG.md

@@ -9,6 +9,7 @@
 ### Changed
 
 - Python 3.9+ is required [#152](https://github.com/python-backoff/backoff/pull/152)
+- Simplify `expo`, `decay` and `fibo` wait generators [#183](https://github.com/python-backoff/backoff/pull/183)
 
 ### Fixed
 

backoff/_wait_gen.py

@@ -24,14 +24,13 @@ def expo(
     """
     # Advance past initial .send() call
     yield 0
-    base_n: float = 1
+
+    a = factor
+    while max_value is None or a < max_value:
+        yield a
+        a *= base
     while True:
-        a = factor * base_n
-        if max_value is None or a < max_value:
-            yield a
-            base_n *= base
-        else:
-            yield max_value
+        yield max_value
 
 
 def decay(
@@ -52,14 +51,13 @@ def decay(
     """
     # Advance past initial .send() call
     yield 0
-    t = 0
+    a = initial_value
+    min_value = min_value or 0.0
+    while a > min_value:
+        yield a
+        a *= math.exp(-decay_factor)
     while True:
-        a = initial_value * math.e ** (-t * decay_factor)
-        if min_value is None or a > min_value:
-            yield a
-            t += 1
-        else:
-            yield min_value
+        yield min_value
 
 
 def fibo(max_value: int | None = None) -> Generator[int, Any, None]:
@@ -75,17 +73,14 @@ def fibo(max_value: int | None = None) -> Generator[int, Any, None]:
 
     a = 1
     b = 1
+    while max_value is None or a < max_value:
+        yield a
+        a, b = b, a + b
     while True:
-        if max_value is None or a < max_value:
-            yield a
-            a, b = b, a + b
-        else:
-            yield max_value
+        yield max_value
 
 
-def constant(
-    interval: float | Iterable[float] = 1,
-) -> Generator[int | float, Any, None]:
+def constant(interval: float | Iterable[float] = 1) -> Generator[float, Any, None]:
     """Generator for constant intervals.
 
     Args:
@@ -104,10 +99,7 @@ def constant(
         yield val
 
 
-def runtime(
-    *,
-    value: Callable[[Any], float],
-) -> Generator[float, Any, None]:
+def runtime(*, value: Callable[[Any], float]) -> Generator[float, Any, None]:
     """Generator that is based on parsing the return value or thrown
         exception of the decorated method
 

tests/test_wait_gen.py

@@ -1,36 +1,36 @@
-# ruff: file-ignore[float-equality-comparison]
-
 import math
 
+import pytest
+
 import backoff
 
 
 def test_decay() -> None:
     gen = backoff.decay()
     gen.send(None)
     for i in range(10):
-        assert math.e**-i == next(gen)
+        assert math.e**-i == pytest.approx(next(gen))
 
 
 def test_decay_init100() -> None:
     gen = backoff.decay(initial_value=100)
     gen.send(None)
     for i in range(10):
-        assert 100 * math.e**-i == next(gen)
+        assert 100 * math.e**-i == pytest.approx(next(gen))
 
 
 def test_decay_init100_decay3() -> None:
     gen = backoff.decay(initial_value=100, decay_factor=3)
     gen.send(None)
     for i in range(10):
-        assert 100 * math.e ** (-i * 3) == next(gen)
+        assert 100 * math.e ** (-i * 3) == pytest.approx(next(gen))
 
 
 def test_decay_init100_decay3_min5() -> None:
     gen = backoff.decay(initial_value=100, decay_factor=3, min_value=5)
     gen.send(None)
     for i in range(10):
-        assert max(100 * math.e ** (-i * 3), 5) == next(gen)
+        assert max(100 * math.e ** (-i * 3), 5) == pytest.approx(next(gen))
 
 
 def test_expo() -> None:
@@ -102,8 +102,8 @@ def test_constant() -> None:
     gen = backoff.constant(interval=[1, 2.0, 3.25])
     gen.send(None)
     assert next(gen) == 1
-    assert next(gen) == 2.0
-    assert next(gen) == 3.25
+    assert next(gen) == pytest.approx(2.0)
+    assert next(gen) == pytest.approx(3.25)
     assert next(gen, None) is None