Coalesce 0.3

simple Python library with coalesce function and "magic" empty value

Simple Python library with coalesce function and “magic” empty value and others features

Installation

pip install coalesce

Features

UniqueValue

This is a factory of some abstract unique values

Example:

from coalesce import UniqueValue

Yes = UniqueValue(truthful=True)
MayBe = UniqueValue()
IDontKnow = UniqueValue()
Unlikely = UniqueValue()
No = UniqueValue(truthful=False)


def answer_lottery():
    import random
    return random.choice((Yes, MayBe, IDontKnow, Unlikely, No))


print("- Are you hungry?")
hungry_answer = answer_lottery()
try:
    if hungry_answer:
        print("- YES, i would eat an elephant!")
    else:
        print("- I'm fed up...")
except TypeError:
    print("- Well, I want only coffee")


print("- Will you marry me?")
marry_answer = answer_lottery()
if marry_answer == Yes:
    print("- Well, finally, YES!")
elif marry_answer == MayBe:
    print("- Well, only if you really are rich...")
elif marry_answer == IDontKnow:
    print("- I need to think...")
elif marry_answer == Unlikely:
    print("- When the cancer on the mountain whistles.")
elif marry_answer == No:
    print("- Who are you, boy?")

empty

The empty is conrete falsely UniqueValue.

Using in situations, when we want differ None and real “empty” value. For example set a dynamically calculated default value:

from coalesce import empty
from random import randint


def f(value=empty):
    if value == empty:
        value = randint(1,10)
    print('value={}'.format(value))

f()  # value=<random(1,10)>
f(None)  # value=None

coalesce

Function returns first not ignoring value from iterable object. By default ignoring empty value

Example:

from coalesce import coalesce, empty
from random import randint


def f(value=empty):
    value = coalesce([value, randint(1,10)])
    print('value={}'.format(value))

f()  # value=<random(1,10)>
f(None)  # value=None

print coalesce([None, 1, 2], ignore=None, default=-7)  # 1
print coalesce([None, None], ignore=None, default=-7)  # -7

first

Function returns first value from iterable for which the function(value) is truthful from iterable object. Else it returns default value

Example:

from coalesce import first

print first(lambda x: x > 1, [None, 1, 2], default=-7)  # 2
print first(lambda x: x > 2, [None, 1, 2], default=-7)  # -7