optional

A mostly transparent python optional class (works with python 2 and 3)

This was a learning exercise. I have not tested/used this in a project.

Run the tests with 'python3 test_optional.py'.

A couple of implementation details made this harder - 'python3 challenges.py' runs a few tests that hight lights some of them

Install

"pip3 install optional"
or Install by cloning the repo and running "sudo python3 setup.py install"

See if a value is set, if not set one

>>> from optional import optional
>>> optional_value = optional()
>>> optional_value.is_set
False
>>> optional_value = optional_value.set_value('some string')
>>> optional_value
'some string'
>>> optional_value.is_set
True

Using a default value

>>> optional_value = optional(None, default=[])
>>> optional_value
[]
>>> optional_value.is_set
False
>>> optional_value.is_default
True
>>> optional_value.append('some string')
>>> optional_value
['some string']

Optional 'becomes' your value

>>> type(optional([]))
<class 'optional.optional([])'>
>>> isinstance(optional([]), list)
True

>>> type(optional('some string'))
<class 'optional.optional(some string)'>
>>> isinstance(optional('some string'), str)
True

>>> optional_value = optional('some string')
>>> optional_value
'some string'
>>> optional_value.is_set
True
>>> optional_value.is_default
False
>>> optional_value = optional_value.set_value(10)
>>> optional_value
10

Fedup of:

>>> def foo(optional_list=None):
...     optional_list = optional_list if optional_list is not None else []
...     print(optional_list)
... 
>>> foo()
[]

Instead try:

>>> def foo(optional_list=None):
...     optional_list = optional(optional_list, default=[])
...     print(optional_list)
... 
>>> foo()
[]
>>> foo([1,2,3])
[1, 2, 3]

Your own Classes will work too

>>> class CustomClass(object):
...     def __init__(self, random, signature, of_custom_class):
...         pass
...     var = 'class data'
... 
>>> optional_value = optional(CustomClass(1,2,3))
>>> optional_value
<optional.optional(<__main__.CustomClass object at 0x102107668>) object at 0x1021076a0>
>>> optional_value.var
'class data'