pysweet-func

test codecov Documentation Status PyPI version

Why pysweet?

Consider the following variants of the same logic:

acc = []

for x in range(10):
    y = x + 1

    if y % 2 == 0:
        acc.extend([y, y * 2])

acc = [
    z for y in (x + 1 for x in range(10))
    for z in [y, y * 2] if y % 2 == 0
]

from itertools import chain

acc = list(chain.from_iterable(map(
    lambda x: [x, x * 2],
    filter(
        lambda x: x % 2 == 0,
        map(lambda x: x + 1, range(10)),
    ),
)))

  • The imperative style can grow complex as requirements evolve;

  • The comprehension style can get complicated when nested;

  • The functional style is not very readable in Python.

In JavaScript, the same logic can be written:

acc = [...Array(10).keys()]
    .map(x => x + 1)
    .filter(x => x % 2 === 0)
    .flatMap(x => [x, x * 2])

Can we write analogous code in Python?

Now you can with pysweet!

from pysweet import Iterable_

acc = (
    Iterable_(range(10))
    .map(lambda x: x + 1)
    .filter(lambda x: x % 2 == 0)
    .flat_map(lambda x: [x, x * 2])
    .to_list()
)

pysweet also offers many other similar features.

pysweet is:

  • lightweight, with around 100 lines of code;

  • mostly syntactic sugar, so it is performant, easy to debug, and easy to learn;

  • successfully used in production.

Sweeten Python with pysweet!

Sample features

  • Iterable with method chaining, in the spirit of JavaScript and Scala:

from pysweet import Iterable_

(
    Iterable_([1, 2])
    .map(lambda x: x + 1)
    .to_list()
)
# [2, 3]

  • Multi-expression lambda, common in modern languages:

from pysweet import block_

val = lambda: block_(
    x := 1,
    x + 1,
)
# val() == 2

  • Statement as expression, in the spirit of Scala and Haskell (if_ is also the ternary operator):

from pysweet import if_, try_, raise_

if_(
    True,
    lambda: 1,
    lambda: 2,
)
# 1

try_(
    lambda: raise_(Exception('test')),
    catch=lambda e: str(e),
)
# 'test'

Next steps