reduce-ex

n-ary reduce operator with support for prefix/suffix elements. Intermediate results are yielded as well. Like functools.reduce but more powerful.

Key Features

• N-ary operation support: Works with functions of any arity (n ≥ 2)
• Intermediate results yielded: Not just the last result is returned
• Flexible input: Supports prefix/suffix elements for initialization/termination
• Memory efficient: Uses bounded deque for argument handling
• Zero Dependencies: Works with stock Python 2+

Usage

Basic Usage

For binary operations (n=2), reduce_ex maintains identical left-associative evaluation order as functools.reduce, while yielding intermediate results:

from reduce_ex import reduce_ex

for partial_sum in reduce_ex(lambda a, b: a + b, range(1, 5)):
    print(partial_sum)
# Computation steps:
# 1+2 = 3
# 3+3 = 6
# 6+4 = 10
# Yields: 3, 6, 10

N-ary Operation (n=3)

For n-ary operations, the evaluation proceeds via left-associative sliding windows:

from reduce_ex import reduce_ex

# Polynomial recurrence: a * b + c
for partial_result in reduce_ex(lambda a, b, c: a * b + c, [2, 3, 4, 5, 6], n=3):
    print(partial_result)
# Computation steps:
# 2 * 3 + 4 = 10
# 10 * 5 + 6 = 56
# Yields: 10, 56

With prefix

from math import tanh

from reduce_ex import reduce_ex

W_h = 0.5
W_x = 0.5
B = 0.5


# Simulate an RNN cell
def rnn_cell(h_prev, x):
    global W_h, W_x, B
    
    return tanh(W_h * h_prev + W_x * x + B)


h_0 = 0.0

for i, h_i in enumerate(
    reduce_ex(
        rnn_cell,
        [0.1, 0.2, 0.3],
        prefix=[h_0]
    ),
    start=1
):
    print(f"Hidden state {i}: {h_i}")

With prefix and suffix

from reduce_ex import reduce_ex

for partial_sum in reduce_ex(lambda a, b: a + b, range(5), prefix=(1, 2), suffix=(10,)):
    print(partial_sum)
# Computation steps:
# 1 + 2 = 3
# 3 + 0 = 3
# 3 + 1 = 4
# 4 + 2 = 6
# 6 + 3 = 9
# 9 + 4 = 13
# 13 + 10 = 23
# Yields: 3, 3, 4, 6, 9, 13, 23

How It Works

The reducer maintains the following invariants:

• Consumes n elements.
• Calls function, yields result, uses the previous result as first argument, and consumes (n-1) more elements.
• Calls function, yields result, uses the previous result as first argument, and consumes (n-1) more elements.
• ...

API Reference

reduce_ex(function, iterable, n=2, prefix=(), suffix=())

• function: Callable of arity n
• iterable: Input elements
• n: Operation arity (must be ≥ 2)
• prefix: Elements prepended to input
• suffix: Elements appended to input

Contributing

Contributions are welcome! Please submit pull requests or open issues on the GitHub repository.

License

This project is licensed under the MIT License.