box¶

class pythonic_fp.gadgets.box.Box¶

Bases: Generic

Box

Container holding at most one item of a given type.

Tip

Objects of the Box type

Are truthy if not empty.
Can be combined with other iterators before being filled.
Can be used like a promise.
Can be used in Python match statements.
Threadsafe

__init__(item: T) → None¶

__init__() → None

Initializer

Initialize Box with 0 or 1 items.

param item:: An optional initial item for the Box.

__bool__() → bool¶: Bool

Truthy if not empty.

__iter__() → Iterator¶

iter

yields:: Boxed item.

__len__() → int¶

Length

1 if Box contains an item
0 if Box is empty

returns:: The number of items currently in the Box.

__eq__(other: object) → bool¶

Equality comparison

Efficiently compare Box to another object.

param other:: The object to be compared.
returns:: True if other is another Box containing an object which compares as equal to the item contained in the Box, otherwise False.

__repr__() → str¶

repr string

Construct string ‘Box()’ if empty, otherwise ‘Box(item_repr)’ where item_repr = repr(item) for the currently contained item.

returns:: A string to reproduce the current state of the Box.

__str__() → str¶

user string

Construct string ‘Box()’ if empty, otherwise ‘Box(item_str)’ where item_str = str(item) for the currently contained item.

returns:: A user meaningful string to represent the current state of the Box.

get() → T¶

get(alt: T) → T

Get

Return the boxed item, if it exists, otherwise an alternate item, if given.

param alt:: An optional item of type T to return if the Box is empty.
returns:: Contents of Box or an alternate item, if given, when the Box is empty.
raises ValueError:: When the alt item is not provided but needed.

pop() → T¶

Pop

Pop item from Box if not empty.

returns:: The item contained in the Box.
raises ValueError:: If Box is empty.

push(item: T) → None¶

Push

Push an item into Box if empty.

param item:: Item to push into the empty Box.
raises ValueError:: If Box is not empty.

put(item: T) → None¶: Put

Put an item in the Box. Discard any previous contents.

exchange(new_item: T) → T¶

Exchange

Exchange an item with what is in the Box.

param new_item:: New item to exchange for current item.
returns:: Original contents of the Box.
raises ValueError:: If Box is empty.

map(f: Callable[[T], U]) → Box¶

Map

Map function f over contents. We need to return a new instance since the type of Box can change.

param f:: Mapping function.
returns:: New instance.

bind(f: Callable[[T], Box]) → Box¶

Bind

Flatmap Box with function f.

param f:: Binding function.
returns:: New instance.