fp-functions

fp-functions is a small Python library to add some features and syntax from functional programming languages. It supports combining functions with the left shift (<<) operator and stacking function calls on an iterable with the pipe (|) operator.

This library requires Python 3

Note that all functions created with Pipe, custom and those from the library, can be called as regular functions

Installation

pip3 install fp-functions

Examples

Examples of the pipe operator:

Finding the squares of all numbers less than 100, excluding the multiples of 7:

from fp_functions import select, where, as_list

print(
    range(100)
    | select(lambda x: x**2)
    | where(lambda x: x % 7 != 0)
    | as_list()
)

# Returns [1, 4, 9, 16, 25, 36, 64, 81]

Finding all distinct permutations of the list [1, 5, 3, 6, 8], with the even numbers replaced with 7 and 9:

from fp_functions import distinct_permutations, replace, as_set

print(
    [5, 6, 8]
    | replace(lambda x: x % 2 == 0, [7, 9])
    | distinct_permutations(2)
    | as_set()
)

# Returns {(7, 7), (9, 9), (5, 7), (7, 9), (9, 5), (5, 9), (7, 5), (9, 7)}

Examples of the function combination:

Create a compound function to return the iterable reversed, with all elements sqrt-ed and as a list

from fp_functions import reversed, select, as_list

reversed_sqrts_list = reversed() >> select(lambda x: x**0.5) >> as_list()
print(reversed_sqrts_list(range(10)))

# Returns [2.0, 1.7320508075688772, 1.4142135623730951, 1.0, 0.0]

This is equivalent to doing the code below, but the function can be used multiple times:

print(
    range(5)
    | reversed()
    | select(lambda x: x**0.5)
    | as_list()
)

# Returns [2.0, 1.7320508075688772, 1.4142135623730951, 1.0, 0.0]

Custom pipe/compund functions:

from fp_functions import Pipe

@Pipe
def select_every_third(iterable):
    count = 0
    for i in iterable:
        if count % 3 == 0:
            yield i
        count += 1

print(
    range(20)
    | select_every_third()
    | as_list()
)

# Returns [0, 3, 6, 9, 12, 15, 18]