Optional variables in Python

Question

do you guys know if there exists a Python equivalent to boost::optional in C++ (or std::optional since C++11: http://en.cppreference.com/w/cpp/utility/optional), i.e. a library that handles semantically optional variables?

I know how to implement it myself or use the other solutions (like foo = (bar, True) which I find ugly and unreadable). Just curious if there is an existing solution.

When you say optional. Is what you really mean is the maybe monad ? — Benjamin Gruenbaum
– Benjamin Gruenbaum, Commented Oct 12, 2013 at 21:28

Sneftel · Accepted Answer · 2013-10-12 21:28:07Z

8

Optional variables, a limited form of algebraic typing, are primarily useful in statically typed languages. In dynamically typed languages like Python, there's no real need for them. As arshajii said, you can use None (or, if you prefer, any other sentinel you'd like) to represent an absent value. You then just check whether the variable has the expected type or not.

answered Oct 12, 2013 at 21:28

Sneftel

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3 Comments

etham Over a year ago

c++ optional and None default value has a real different semantics. Supposing the value I want to store in an optional variable can already hold the None type, how can I check if this optional variable has been set ?

Sneftel Over a year ago

@etham Well, ideally you'd fix your overly complicated data model. But if you insisted on it, you could simply use (for instance) a one-element tuple to wrap the value.

etham Over a year ago

You are right. A language with too much features prevent us from having a nice design. I fixed my data model ;)

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