Tuple Sum Filter

A library to play with filtering numeric sequences by sums of their pairs, triplets, etc.

Comes with a bonus CLI to demo the functionality.

Requires (and CI tests on) python 3.8 to 3.10.
If you need to use python 3.7 then try replacing
math.prod(some_iterable) with functools.reduce(lambda x, y: x * y, some_iterable)


We’re thinking of this mostly as a library with the CLI as only for demo purposes.
Ways you can see this in the code:

  • logging should really handled by the consumer,
    • our get_logger should be something that is passed into the lib
  • the CLI is pretty light on automated tests
  • we use pretty loose production dependency pinning
    • rather than pip freeze > requirements.txt of a deployed app
    • we want to keep things loose so that consumers can keep installing us alongside other things
    • we should probably set up tox/nox test runs against v.latest of our dependencies

Running the demo

in a fresh virtualenv (python>=3.8)

# install project and deps
pip install git+https://github.com/lbillingham/tuple-sum-filter.git

# create a suitable input file
echo "1721\n979\n366\n299\n675\n1456\n" > example.txt

# run the demo
filter_demo --input_file=example.txt --sum_target=2020 --dimension=2

you should see output like

checking for pairs of numbers that sum to 2020 in example.txt
Results pair (1721, 299) match: sum to 2020 and multiply to 514579

Consuming the library

The main filtering functions are pairs_that_sum_to and triplets_that_sum_to.
They both have signatures (numbers: Sequence[int|float], sum_target: int|float) -> things_that_passed_the_filter list[tuple].

There is also a file-reading helper numbers_in_file exported at the top level.


Run the following to install the project (and dev dependencies) into your active virtualenv:

make dev_install

day-to-day development tasks can be orchestrated via make

  • dependency management
  • test/lint/typecheck running
  • coverage reporting
  • run make without any arguments to see a list

There is a CI suite which runs lint and test on several python versions.
We don’t run typechecking as a gate in CI because we think that
turns a sometimes-useful tool into a Goodhart target.


We have not been optimizing for performance and it kind of shows.

When we run the benchmarking suite we see ~0.4 seconds fairly consistently for the triplet/3D problem.

We have at least 3 ideas of how to speed things up: several of them include dropping floating-point support.

$ make benchmark

tests/performance_check.py ..                                                                                                                                [100%]

------------------------------------------------------------------------------------- benchmark: 2 tests ------------------------------------------------------------------------------------
Name (time in ms)             Min                 Max                Mean            StdDev              Median               IQR            Outliers       OPS            Rounds  Iterations
test_input1_pairs          5.4665 (1.0)        6.2297 (1.0)        5.6687 (1.0)      0.1018 (1.0)        5.6575 (1.0)      0.1289 (1.0)          47;3  176.4077 (1.0)         172           1
test_input1_triplets     384.6154 (70.36)    386.5000 (62.04)    385.4776 (68.00)    0.8287 (8.14)     385.4333 (68.13)    1.5047 (11.67)         2;0    2.5942 (0.01)          5           1

? ✂️ cookiecut from lbillingham’s python-cli-template


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