"""Functions that operate on lists and dicts.
.. versionadded:: 1.0.0
"""
from __future__ import absolute_import
import random
import pydash as pyd
from .helpers import itercallback, iterator, call_callback, NoValue
__all__ = (
'all_',
'any_',
'at',
'collect',
'contains',
'count_by',
'deep_pluck',
'detect',
'each',
'each_right',
'every',
'filter_',
'find',
'find_last',
'find_where',
'foldl',
'foldr',
'for_each',
'for_each_right',
'group_by',
'include',
'index_by',
'inject',
'invoke',
'map_',
'mapiter',
'max_',
'min_',
'partition',
'pluck',
'reduce_',
'reduce_right',
'reductions',
'reductions_right',
'reject',
'sample',
'select',
'shuffle',
'size',
'some',
'sort_by',
'to_list',
'where',
)
[docs]def at(collection, *indexes): # pylint: disable=invalid-name
"""Creates a list of elements from the specified indexes, or keys, of the
collection. Indexes may be specified as individual arguments or as arrays
of indexes.
Args:
collection (list|dict): Collection to iterate over.
indexes (mixed): The indexes of `collection` to retrieve, specified as
individual indexes or arrays of indexes.
Returns:
list: filtered list
.. versionadded:: 1.0.0
"""
indexes = pyd.flatten_deep(indexes)
return [collection[i] for i in indexes]
[docs]def contains(collection, target, from_index=0):
"""Checks if a given value is present in a collection. If `from_index` is
negative, it is used as the offset from the end of the collection.
Args:
collection (list|dict): Collection to iterate over.
target (mixed): Target value to compare to.
from_index (int, optional): Offset to start search from.
Returns:
bool: Whether `target` is in `collection`.
See Also:
- :func:`contains` (main definition)
- :func:`include` (alias)
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
collection = collection.values()
else:
# only makes sense to do this if `collection` is not a dict
collection = collection[from_index:]
return target in collection
include = contains
[docs]def count_by(collection, callback=None):
"""Creates an object composed of keys generated from the results of running
each element of `collection` through the callback.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
dict: Dict containing counts by key.
.. versionadded:: 1.0.0
"""
ret = {}
for result in itercallback(collection, callback):
ret.setdefault(result[0], 0)
ret[result[0]] += 1
return ret
[docs]def deep_pluck(collection, path):
"""Like pluck but works with deep paths.
Args:
collection (list|dict): list of dicts
path (str|list): collection's path to pluck
Returns:
list: plucked list
.. versionadded:: 2.2.0
"""
return map_(collection, pyd.deep_property(path))
[docs]def every(collection, callback=None):
"""Checks if the callback returns a truthy value for all elements of a
collection. The callback is invoked with three arguments:
``(value, index|key, collection)``. If a property name is passed for
callback, the created :func:`pluck` style callback will return the property
value of the given element. If an object is passed for callback, the
created :func:`where` style callback will return ``True`` for elements that
have the properties of the given object, else ``False``.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
bool: Whether all elements are truthy.
See Also:
- :func:`every` (main definition)
- :func:`all_` (alias)
.. versionadded:: 1.0.0
"""
if callback:
cbk = pyd.iteratee(callback)
collection = [cbk(item) for item in collection]
return all(collection)
all_ = every
[docs]def filter_(collection, callback=None):
"""Iterates over elements of a collection, returning an list of all
elements the callback returns truthy for.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list: Filtered list.
See Also:
- :func:`select` (main definition)
- :func:`filter_` (alias)
.. versionadded:: 1.0.0
"""
return [value
for is_true, value, _, _ in itercallback(collection, callback)
if is_true]
select = filter_
[docs]def find(collection, callback=None):
"""Iterates over elements of a collection, returning the first element that
the callback returns truthy for.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
mixed: First element found or ``None``.
See Also:
- :func:`find` (main definition)
- :func:`detect` (alias)
- :func:`find_where` (alias)
.. versionadded:: 1.0.0
"""
search = (collection[key]
for is_true, _, key, _ in itercallback(collection, callback)
if is_true)
return next(search, None)
detect = find
find_where = find
[docs]def find_last(collection, callback=None):
"""This method is like :func:`find` except that it iterates over elements
of a `collection` from right to left.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
mixed: Last element found or ``None``.
.. versionadded:: 1.0.0
"""
search = (collection[key]
for is_true, _, key, _ in itercallback(collection,
callback,
reverse=True)
if is_true)
return next(search, None)
[docs]def for_each(collection, callback=None):
"""Iterates over elements of a collection, executing the callback for each
element.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list|dict: `collection`
See Also:
- :func:`for_each` (main definition)
- :func:`each` (alias)
.. versionadded:: 1.0.0
"""
next((None for ret, _, _, _ in itercallback(collection, callback)
if ret is False),
None)
return collection
each = for_each
[docs]def for_each_right(collection, callback):
"""This method is like :func:`for_each` except that it iterates over
elements of a `collection` from right to left.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list|dict: `collection`
See Also:
- :func:`for_each_right` (main definition)
- :func:`each_right` (alias)
.. versionadded:: 1.0.0
"""
next((None for ret, _, _, _ in itercallback(collection,
callback,
reverse=True)
if ret is False),
None)
return collection
each_right = for_each_right
[docs]def group_by(collection, callback=None):
"""Creates an object composed of keys generated from the results of running
each element of a `collection` through the callback.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
dict: Results of grouping by `callback`.
.. versionadded:: 1.0.0
"""
ret = {}
cbk = pyd.iteratee(callback)
for value in collection:
key = cbk(value)
ret.setdefault(key, [])
ret[key].append(value)
return ret
[docs]def index_by(collection, callback=None):
"""Creates an object composed of keys generated from the results of running
each element of the collection through the given callback.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
dict: Results of indexing by `callback`.
.. versionadded:: 1.0.0
"""
ret = {}
cbk = pyd.iteratee(callback)
for value in collection:
ret[cbk(value)] = value
return ret
[docs]def invoke(collection, method_name, *args, **kargs):
"""Invokes the method named by `method_name` on each element in the
`collection` returning a list of the results of each invoked method.
Args:
collection (list|dict): Collection to iterate over.
method_name (str): Name of method to invoke.
args (optional): Arguments to pass to method call.
kargs (optional): Keyword arguments to pass to method call.
Returns:
list: List of results of invoking method of each item.
.. versionadded:: 1.0.0
"""
lst = []
for item in collection:
if callable(method_name):
lst.append(method_name(item, *args, **kargs))
else:
lst.append(getattr(item, method_name)(*args, **kargs))
return lst
[docs]def map_(collection, callback=None):
"""Creates an array of values by running each element in the collection
through the callback. The callback is invoked with three arguments:
``(value, index|key, collection)``. If a property name is passed for
callback, the created :func:`pluck` style callback will return the property
value of the given element. If an object is passed for callback, the
created :func:`where` style callback will return ``True`` for elements that
have the properties of the given object, else ``False``.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list: Mapped list.
See Also:
- :func:`map_` (main definition)
- :func:`collect` (alias)
.. versionadded:: 1.0.0
"""
return list(mapiter(collection, callback))
collect = map_
[docs]def mapiter(collection, callback=None):
"""Like :func:`map_` except returns a generator.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
generator: Each mapped item.
.. versionadded:: 2.1.0
"""
for result in itercallback(collection, callback):
yield result[0]
[docs]def max_(collection, callback=None):
"""Retrieves the maximum value of a `collection`.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
mixed: Maximum value.
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
collection = collection.values()
return max(collection, key=pyd.iteratee(callback))
[docs]def min_(collection, callback=None):
"""Retrieves the minimum value of a `collection`.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
mixed: Minimum value.
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
collection = collection.values()
return min(collection, key=pyd.iteratee(callback))
[docs]def partition(collection, callback=None):
"""Creates an array of elements split into two groups, the first of which
contains elements the `callback` returns truthy for, while the second of
which contains elements the `callback` returns falsey for. The `callback`
is invoked with three arguments: ``(value, index|key, collection)``.
If a property name is provided for `callback` the created :func:`pluck`
style callback returns the property value of the given element.
If an object is provided for `callback` the created :func:`where` style
callback returns ``True`` for elements that have the properties of the
given object, else ``False``.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list: List of grouped elements.
.. versionadded:: 1.1.0
"""
trues = []
falses = []
for is_true, value, _, _ in itercallback(collection, callback):
if is_true:
trues.append(value)
else:
falses.append(value)
return [trues, falses]
[docs]def pluck(collection, key):
"""Retrieves the value of a specified property from all elements in the
collection.
Args:
collection (list|dict): list of dicts
key (str): collection's key to pluck
Returns:
list: plucked list
.. versionadded:: 1.0.0
"""
return map_(collection, pyd.prop(key))
[docs]def reduce_(collection, callback=None, accumulator=None):
"""Reduces a collection to a value which is the accumulated result of
running each element in the collection through the callback, where each
successive callback execution consumes the return value of the previous
execution.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed): Callback applied per iteration.
accumulator (mixed, optional): Initial value of aggregator. Default is
to use the result of the first iteration.
Returns:
mixed: Accumulator object containing results of reduction.
See Also:
- :func:`reduce_` (main definition)
- :func:`foldl` (alias)
- :func:`inject` (alias)
.. versionadded:: 1.0.0
"""
iterable = iterator(collection)
if accumulator is None:
try:
_, accumulator = next(iterable)
except StopIteration:
raise TypeError(
'reduce_() of empty sequence with no initial value')
result = accumulator
if callback is None:
callback = lambda item, *args: item
for index, item in iterable:
result = call_callback(callback, result, item, index)
return result
foldl = reduce_
inject = reduce_
[docs]def reduce_right(collection, callback=None, accumulator=None):
"""This method is like :func:`reduce_` except that it iterates over
elements of a `collection` from right to left.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed): Callback applied per iteration.
accumulator (mixed, optional): Initial value of aggregator. Default is
to use the result of the first iteration.
Returns:
mixed: Accumulator object containing results of reduction.
See Also:
- :func:`reduce_right` (main definition)
- :func:`foldr` (alias)
.. versionadded:: 1.0.0
"""
if not isinstance(collection, dict):
collection = sorted(collection, reverse=True)
return reduce_(collection, callback, accumulator)
foldr = reduce_right
[docs]def reductions(collection, callback=None, accumulator=None, from_right=False):
"""This function is like :func:`reduce_` except that it returns a list of
every intermediate value in the reduction operation.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed): Callback applied per iteration.
accumulator (mixed, optional): Initial value of aggregator. Default is
to use the result of the first iteration.
Returns:
list: Results of each reduction operation.
Note:
The last element of the returned list would be the result of using
:func:`reduce_`.
.. versionadded:: 2.0.0
"""
if callback is None:
callback = lambda item, *args: item
results = []
def interceptor(result, item, index): # pylint: disable=missing-docstring
result = call_callback(callback, result, item, index)
results.append(result)
return result
reducer = reduce_right if from_right else reduce_
reducer(collection, interceptor, accumulator)
return results
[docs]def reductions_right(collection, callback=None, accumulator=None):
"""This method is like :func:`reductions` except that it iterates over
elements of a `collection` from right to left.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed): Callback applied per iteration.
accumulator (mixed, optional): Initial value of aggregator. Default is
to use the result of the first iteration.
Returns:
list: Results of each reduction operation.
Note:
The last element of the returned list would be the result of using
:func:`reduce_`.
.. versionadded:: 2.0.0
"""
return reductions(collection, callback, accumulator, from_right=True)
[docs]def reject(collection, callback=None):
"""The opposite of :func:`filter_` this method returns the elements of a
collection that the callback does **not** return truthy for.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list: Rejected elements of `collection`.
.. versionadded:: 1.0.0
"""
return [value
for is_true, value, _, _ in itercallback(collection, callback)
if not is_true]
[docs]def sample(collection, n=None):
"""Retrieves a random element or `n` random elements from a `collection`.
Args:
collection (list|dict): Collection to iterate over.
n (int, optional): Number of random samples to return.
Returns:
list|mixed: List of sampled collection value if `n` is provided, else
single value from collection if `n` is ``None``.
.. versionadded:: 1.0.0
"""
num = min(n or 1, len(collection))
sampled = random.sample(collection, num)
return sampled[0] if n is None else sampled
[docs]def shuffle(collection):
"""Creates a list of shuffled values, using a version of the Fisher-Yates
shuffle.
Args:
collection (list|dict): Collection to iterate over.
Returns:
list: Shuffled list of values.
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
collection = collection.values()
# Make copy of collection since random.shuffle works on list in-place.
collection = list(collection)
# NOTE: random.shuffle uses Fisher-Yates.
random.shuffle(collection)
return collection
[docs]def size(collection):
"""Gets the size of the `collection` by returning `len(collection)` for
iterable objects.
Args:
collection (list|dict): Collection to iterate over.
Returns:
int: Collection length.
.. versionadded:: 1.0.0
"""
return len(collection)
[docs]def some(collection, callback=None):
"""Checks if the callback returns a truthy value for any element of a
collection. The callback is invoked with three arguments:
``(value, index|key, collection)``. If a property name is passed for
callback, the created :func:`pluck` style callback will return the property
value of the given element. If an object is passed for callback, the
created :func:`where` style callback will return ``True`` for elements that
have the properties of the given object, else ``False``.
Args:
collection (list|dict): Collection to iterate over.
callbacked (mixed, optional): Callback applied per iteration.
Returns:
bool: Whether any of the elements are truthy.
See Also:
- :func:`some` (main definition)
- :func:`any_` (alias)
.. versionadded:: 1.0.0
"""
if callback:
cbk = pyd.iteratee(callback)
collection = [cbk(item) for item in collection]
return any(collection)
any_ = some
[docs]def sort_by(collection, callback=None):
"""Creates a list of elements, sorted in ascending order by the results of
running each element in a `collection` through the callback.
Args:
collection (list|dict): Collection to iterate over.
callback (mixed, optional): Callback applied per iteration.
Returns:
list: Sorted list.
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
collection = collection.values()
return sorted(collection, key=pyd.iteratee(callback))
[docs]def to_list(collection):
"""Converts the collection to a list.
Args:
collection (list|dict): Collection to iterate over.
Returns:
list: Collection converted to list.
.. versionadded:: 1.0.0
"""
if isinstance(collection, dict):
ret = collection.values()
else:
ret = list(collection)
return ret
[docs]def where(collection, properties):
"""Examines each element in a collection, returning an array of all
elements that have the given properties.
Args:
collection (list|dict): Collection to iterate over.
properties (dict): property values to filter by
Returns:
list: filtered list.
.. versionadded:: 1.0.0
"""
return filter_(collection, pyd.matches(properties))