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 3.4+ and pypy3.

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, 2)

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:

Running tests

To run the tests using your default python:

pip install -r test_requirements.txt
pytest

To fully run tox you need all the supported pythons to be installed. These are 3.4+ and PyPy3. You can run it for particular environment even in absense of all of the above:

tox -e py310
tox -e pypy3
tox -e lint

Release files for funcy 2.1

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for funcy 2.1
File	Size	Uploaded
funcy-2.1.tar.gz	981.2 kB	Sep 10, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for funcy 2.1
File	Interpreter	ABI	Platform	Reset
funcy-2.1-py3-none-any.whl 29.3 kB Sep 10, 2026	Python 3	none	any	Details

Total release size: 1.0 MB

Release files / funcy-2.1.tar.gz

Download URL	funcy-2.1.tar.gz
Size	981.2 kB
Tags	Source
SHA-256 checksum How to use checksums	`8979feb3de7120afd1d00e5a8eae810c1942e4bfbc91697151e9ee1e49f79284`
BLAKE2b-256 checksum How to use checksums	`032cc704bc76973088cb17b663a467aab7e2d46a999d647116db145daa2121ed`
Upload date	Sep 10, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/7.0.0 CPython/3.14.3`

Release files / funcy-2.1-py3-none-any.whl

Download URL	funcy-2.1-py3-none-any.whl
Size	29.3 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`290794186530c944f7e444d2e28b98f33a55685f2bfb9b7a61dac564decab8f8`
BLAKE2b-256 checksum How to use checksums	`8c5b02e0c095105b0c8a26f122d1ec312731008b914814d172dd3ee81e851642`
Upload date	Sep 10, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`twine/7.0.0 CPython/3.14.3`