If a function does not have a return statement, is it valid?

[HimaniBansal]

Is it appropriate to say that a function not having a return statement is valid?

[Sheetal_1]

Very conveniently. A function that doesn’t return anything returns a None object. In python, Not necessarily does the return keyword mark the end of a function it merely ends it when present in the function. Normally, a block of code marks a function and where it ends, the function body ends.

[vegaseat]

I could think of valid functions that perform an action, like formated printing. No need to return anything.

[JamesCherrill]

My background is in Smalltalk, so I can't understand the design decision to return None/void from a method/function that has no specific return value.
In Smalltalk a method with no explicit return wil always return the receiver object, which enables you to chain calls together like (pseudocode)
person.setName(etc).setAddress(etc).setDOB(etc).print()
Interestingly, Java under Oracle's management has recognised this and the latest APIs tend to return this; so calls can be chanied. It's called a "fluent interface" after Martin Fowler (2005)

[vegaseat]

Is this because Smalltalk is totally Object Oriented?
With Python you can use a number of different programming styles.

[JamesCherrill]

Yes, Smalltalk is totally OO, all it has are objects and messages. Blocks of code are just objects. The language doesn't even have loops or if tests - the same functionality is built with messages to Boolean objects, eg (pseudocode)
aBoolean.ifTrue(some code).ifFalse(some code) or aBoolean.whileTrue(some code)

But I think thats a different point from the default return value in Java etc. Returning this/self makes chaining calls easier and costs nothing. As far as I can see it's not too late - you could change Java to return this from void methods and it wouldn't break any existng code.