option.py is an attempt to duplicate the functionality of Scala's Option class in Python, because doing it in PHP and Javascript isn't enough. Options are represented by either an instance of Some containing the value or the singleton Nothing() (since None was naturally taken).

Create a Some instance based upon a value like so: opt = Some("my option")

Note that passing a non-value to Some will work:

>>> s = Some(None)
>>> s.get() is None)
True

If you want to avoidNone)-checking, the Option constructor will do that for you:

>>> OptionNone))
<option.Nothing object at 0x10ea50290>
>>> Option("an option")
<option.Some object at 0x10ea50190>

You can get the value:

opt.get()                                            # -> "my option"
opt.getOrElse("default")                             # -> "my option"
Nothing().get()                                      # -> Exception thrown
Nothing().getOrElse("default")                       # -> "default"

Get an Option's status:

opt.isEmpty()    # -> False
opt.isDefined()  # -> True

None).isEmpty() # -> True None).isDefined() # -> False

Treat the Option like a sequence:

opt.foreach(lambda input: print input)               # print "my option" called
>>> for input in Some(1):
...   print input
... 
"my option"

Nothing().foreach(lambda input: print input)         # nothing called
>>> for i in Nothing():
...   print i
... 

opt.filter(lambda input: input == "my option")       # -> Some("my option")
opt.filter(lambda input: input == "my option!")      # -> Nothing()
Nothing().filter(lambda input: input == "my option") # -> Nothing(), lambda not called

Transform the Option:

opt.map(lambda input: input + "!")                   # -> Some("my option!")
Nothing().map(lambda input: input + "!")             # -> Nothing(), anonymous function not called
opt.flatMap(lambda input: Some(input + "!"))         # -> Some("my option!")
Nothing().flatMap(lambda input: Some(input + "!"))   # -> Nothing(), anonymous function not called

Make sure that the function you pass to flatMap() returns an option:

>>> opt.flatMap(lambda input: input + "!")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "option.py", line 35, in flatMap
    def map(self, f):
Exception: f must return an Option.
>>> opt.flatMap(lambda input: Nothing())
<option.Nothing object at 0x10ea50290>

Options can be used in list comprehensions, but you'll get a list in return:

>>> [input + '!' for input in opt]
['my option!']
>>> [input + '!' for input in Nothing()]
[]

Inheritance:

>>> isinstance(opt, Some)
True
>>> isinstance(opt, Option)
True
>>> isinstance(Nothing(), Nothing)
True
>>> isinstance(Nothing(), Option)
True

Example usage:

def listValueAtPosition(l, position):
	if (position >= 0 and position < len(l)):
		return Some(l[position])
	return Nothing()
listValueAtPosition([1, 2, 3, False, None], 2)       # -> Some("3")
listValueAtPosition([1, 2, 3, False, None], 3)       # -> Some(False)
listValueAtPosition([1, 2, 3, False, None], 4)       # -> Some(None)
listValueAtPosition([1, 2, 3, False, None], 5)       # -> Nothing()

For details on the methods available, see Scala's Option class definition at http://www.scala-lang.org/docu/files/api/scala/Option.html