[Bug]: Inconsistent initial=None Parameter Handling in asyncstdlib.accumulate #176
Description
What happened?
Issue Description
asyncstdlib.accumulate handles the initial=None parameter inconsistently compared to itertools.accumulate. When initial=None is explicitly passed, the two libraries produce different results.
Expected Behavior (itertools.accumulate)
When initial=None is explicitly provided, itertools.accumulate treats it as if no initial value was specified and starts accumulation from the first element of the iterable.
Actual Behavior (asyncstdlib.accumulate)
When initial=None is explicitly provided, asyncstdlib.accumulate treats None as a literal initial value and includes it in the accumulation sequence.
Minimal Reproducible Example
import asyncstdlib
import itertools
async def async_gen():
"""Async generator: yields 1, 2, 3"""
for i in [1, 2, 3]:
yield i
def sync_gen():
"""Sync generator: yields 1, 2, 3"""
for i in [1, 2, 3]:
yield i
def safe_accumulator(x, y):
"""Accumulator that can handle None values"""
if x is None:
return y
return x + y
# Test itertools.accumulate with initial=None (expected behavior)
print("=== itertools.accumulate with initial=None ===")
result_itertools = list(itertools.accumulate(sync_gen(), safe_accumulator, initial=None))
print(f"Result: {result_itertools}")
print("\n=== asyncstdlib.accumulate with initial=None ===")
async def test_asyncstdlib():
result = []
async for item in asyncstdlib.accumulate(async_gen(), safe_accumulator, initial=None):
result.append(item)
return result
result_asyncstdlib = await test_asyncstdlib()
print(f"Result: {result_asyncstdlib}")
print(f"\nResults match: {result_itertools == result_asyncstdlib}")
print(f"itertools result: {result_itertools}")
print(f"asyncstdlib result: {result_asyncstdlib}")
# Show the difference clearly
if result_itertools != result_asyncstdlib:
print("\n🔴 INCONSISTENCY DETECTED:")
print(f" itertools treats initial=None as 'no initial value': {result_itertools}")
print(f" asyncstdlib treats initial=None as literal None value: {result_asyncstdlib}")
else:
print("\n✅ Results are consistent")Output:
=== itertools.accumulate with initial=None ===
Result: [1, 3, 6]
=== asyncstdlib.accumulate with initial=None ===
Result: [None, 1, 3, 6]
Results match: False
itertools result: [1, 3, 6]
asyncstdlib result: [None, 1, 3, 6]
🔴 INCONSISTENCY DETECTED:
itertools treats initial=None as 'no initial value': [1, 3, 6]
asyncstdlib treats initial=None as literal None value: [None, 1, 3, 6]
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