Funcy 
A collection of fancy functional tools focused on practicality.
Inspired by clojure, underscore and my own abstractions. Keep reading to get an overview or read the docs. Or jump directly to cheatsheet.
Works with Python 2.7, 3.4+ and pypy.
Installation
pip install funcy
Overview
Import stuff from funcy to make things happen:
from funcy import whatever, you, need
Merge collections of same type (works for dicts, sets, lists, tuples, iterators and even strings):
merge(coll1, coll2, coll3, ...)
join(colls)
merge_with(sum, dict1, dict2, ...)
Walk through collection, creating its transform (like map but preserves type):
walk(str.upper, {'a', 'b'}) # {'A', 'B'}
walk(reversed, {'a': 1, 'b': 2}) # {1: 'a', 2: 'b'}
walk_keys(double, {'a': 1, 'b': 2}) # {'aa': 1, 'bb': 2}
walk_values(inc, {'a': 1, 'b': 2}) # {'a': 2, 'b': 3}
Select a part of collection:
select(even, {1,2,3,10,20}) # {2,10,20}
select(r'^a', ('a','b','ab','ba')) # ('a','ab')
select_keys(callable, {str: '', None: None}) # {str: ''}
compact({2, None, 1, 0}) # {1,2}
Manipulate sequences:
take(4, iterate(double, 1)) # [1, 2, 4, 8]
first(drop(3, count(10))) # 13
lremove(even, [1, 2, 3]) # [1, 3]
lconcat([1, 2], [5, 6]) # [1, 2, 5, 6]
lcat(map(range, range(4))) # [0, 0, 1, 0, 1, 2]
lmapcat(range, range(4)) # same
flatten(nested_structure) # flat iter
distinct('abacbdd') # iter('abcd')
lsplit(odd, range(5)) # ([1, 3], [0, 2, 4])
lsplit_at(2, range(5)) # ([0, 1], [2, 3, 4])
group_by(mod3, range(5)) # {0: [0, 3], 1: [1, 4], 2: [2]}
lpartition(2, range(5)) # [[0, 1], [2, 3]]
chunks(2, range(5)) # iter: [0, 1], [2, 3], [4]
pairwise(range(5)) # iter: [0, 1], [1, 2], ...
And functions:
partial(add, 1) # inc
curry(add)(1)(2) # 3
compose(inc, double)(10) # 21
complement(even) # odd
all_fn(isa(int), even) # is_even_int
one_third = rpartial(operator.div, 3.0)
has_suffix = rcurry(str.endswith)
Create decorators easily:
@decorator
def log(call):
print call._func.__name__, call._args
return call()
Abstract control flow:
walk_values(silent(int), {'a': '1', 'b': 'no'})
# => {'a': 1, 'b': None}
@once
def initialize():
"..."
with suppress(OSError):
os.remove('some.file')
@ignore(ErrorRateExceeded)
@limit_error_rate(fails=5, timeout=60)
@retry(tries=2, errors=(HttpError, ServiceDown))
def some_unreliable_action(...):
"..."
class MyUser(AbstractBaseUser):
@cached_property
def public_phones(self):
return self.phones.filter(public=True)
Ease debugging:
squares = {tap(x, 'x'): tap(x * x, 'x^2') for x in [3, 4]}
# x: 3
# x^2: 9
# ...
@print_exits
def some_func(...):
"..."
@log_calls(log.info, errors=False)
@log_errors(log.exception)
def some_suspicious_function(...):
"..."
with print_durations('Creating models'):
Model.objects.create(...)
# ...
# 10.2 ms in Creating models
And much more.
Dive in
Funcy is an embodiment of ideas I explain in several essays:
- Why Every Language Needs Its Underscore
- Functional Python Made Easy
- Abstracting Control Flow
- Painless Decorators
Running tests
To run the tests using your default python:
pip install -r test_requirements.txt py.test
To fully run tox you need all the supported pythons to be installed. These are 2.6+, 3.3+, PyPy and PyPy3. You can run it for particular environment even in absense of all of the above:
tox -e py27 tox -e py36 tox -e lint
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