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.

Works with Python 2.6, 2.7, 3.3 (experimental) and pypy.

Installation

pip install funcy

Overview

Just import stuff from funcy to make things happen:

from funcy import * # or whatever you need

Merge collections of same type (works for dicts, sets, lists, tuples, iterators and even strings):

merge(coll1, coll2, coll3, ...)
join(colls)

Walk through collection, creating it's 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, '', 0})                    # {2,'',0}

Test collection contents:

all(callable, [abs, open, int]) # True
all(even, [1, 2, 5])            # False
any(even, [1, 2, 5])            # True
none(even, [1, 2, 5])           # False
is_distinct('adbec')            # True

Or search for something:

some(even, [1, 2, 5])      # 2
some([0, '', -1, None, 2]) # -1

More tools for mappings:

flip({'a': 1, 'b': 2})                        # {1: 'a', 2: 'b'}
project({'a': 1, 'b': 2, 'c': 3}, ['a', 'c']) # {'a': 1, 'c': 3}
pluck('a', [{'a': 1, 'b': 2}, {'a': 10}])     # [1, 10]
where([{'a': 1, 'b': 2}, {'a': 10}], a=1)     # [{'a': 1, 'b': 2}]

Manipulate functions:

partial(add, 1)                # inc
curry(add)(1)(2)               # 3
compose(inc, double)(10)       # 21
complement(even)               # odd
map(iffy(len), ['ab',None,'c'] # [2,None,1]
iffy(callable, caller())(val)  # val() if callable(val) else val

Easy decorators:

@decorator
def log(call):
    print call._func.__name__, call._args
    return call()

Work with sequences:

take(4, iterate(double, 1)) # [1, 2, 4, 8]
first(drop(3, count(10)))   # 13

remove(even, [1, 2, 3])     # [1, 3]
concat([1, 2], [5, 6])      # [1, 2, 5, 6]
cat(map(range, range(4)))   # [0, 0, 1, 0, 1, 2]
mapcat(range, range(4)))    # same
distinct('abacbdd')         # list('abcd')

split(odd, range(5))        # [[1, 3], [0, 2, 4]]
split_at(2, range(5))       # [[0, 1], [2, 3, 4]]
group_by(mod3, range(5))    # {0: [0, 3], 1: [1, 4], 2: [2]}

partition(2, range(5))      # [[0, 1], [2, 3]]
chunks(2, range(5))         # [[0, 1], [2, 3], [4]]
partition(2, 1, range(4))   # [[0, 1], [1, 2], [2, 3]]
chunks(2, 1, range(4))      # [[0, 1], [1, 2], [2, 3], [3]]

And many more.

How you can help

Bring your ideas and/or code that can make functional python more fun.

TODO

• create cheatsheet html
• reject*(), disjoint*() collections
• merge_with(), zip_with()
• starfilter()
• one argument select*()? other name?
• reversed() to work with iterators?
• vector chained boolean test (like perl 6 [<])