Python has implemented map, filter etc. as functions, rather than methods on a sequence. This makes the result harder to read and iterators less used than they could be. iterpy exists to change that.

You get this 🔥:

from iterpy import Iter

result = Iter([1,2,3]).map(multiply_by_2).filter(is_even)

Instead of this:

sequence = [1,2,3]
multiplied = [multiply_by_2(x) for x in sequence]
result = [x for x in multiplied if is_even(x)]

Or this:

result = filter(is_even, map(multiply_by_2, [1,2,3]))

pip install iterpy

from iterpy import Iter

result = (Iter([1, 2])
            .filter(lambda x: x % 2 == 0)
            .map(lambda x: x * 2)
            .to_list()
)
assert result == [4]

iterpy stands on the shoulders of Scala, Rust etc.

Other Python projects have had similar ideas:

• PyFunctional has existed for 7+ years with a comprehensive feature set. It is performant, with built-in lineage and caching. Unfortunately, this makes typing non-trivial, with a 4+ year ongoing effort to add types.
• flupy is highly similar, well typed, and mature. I had some issues with .flatten() not being type-hinted correctly, but but your mileage may vary.
• Your library here? Feel free to make an issue if you have a good alternative!

• Make it work: Concise syntax borrowed from Scala, Rust etc.
• Make it right: Fully typed, no exceptions
• Make it fast:
  • Concurrency through .pmap
  • (Future): Caching
  • (Future): Refactor operations to use generators
• Keep it simple: No dependencies

As a heuristic, we follow the APIs of:

• Rust's std::iter
• Rust's itertools

In cases where this conflicts with typical python implementations, the API should be as predictable as possible for Python users.

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