[Tutor] What is Tuple in the typing module?

[C W]

Thank you, Peter and Alan. Both very helpful. I was able to figure it out.
Cheers!

On Sat, Aug 17, 2019 at 5:45 AM Alan Gauld via Tutor <tutor at python.org>
wrote:

> On 17/08/2019 00:46, C W wrote:
>
> The formatting seems messed up I'll try to straighten it out.
> I hope I get it right!
>
> Caveat: I'm no expert in the typing module, I've read the
> docs but never found any use for it.
>
> > What exactly is Tuple in the typing module? What does it do?
>
> It specifies a tuple type. I assume you understand what
> a tuple is in regular Python code?
>
> > This is the definition from its website.
> > https://docs.python.org/3/library/typing.html
> > "A type alias is defined by assigning the type to the alias"
> >
> > I have no idea what that means.
>
> It just means that an alias is a label that you can use
> to signify a type. And you can effectively create new
> "types" by combining simpler types
>
>
> > Here's the example from the documentation:
> >
> > from typing import Dict, Tuple, Sequence
> ConnectionOptions = Dict[str, str]
> Address = Tuple[str,int]Server  = Tuple[Address, ConnectionOptions]
>
> So this creates 3 new type aliases: ConnectionOptions, Address, Server
> which are defined in terms of basic Python types,.
> So Address is a tuple of a string and integer.
>
> > def broadcast_message(message: str, servers: Sequence[Server]) -> None:
>
> Ad this defines a function where the parameter types are
> specified in terms of the new type names that we just
> created.
>
> > # The static type checker will treat the previous type signature as#
> > being exactly equivalent to this one.
>
> > def broadcast_message(
> >         message: str,
> >         servers: Sequence[Tuple[Tuple[str, int], Dict[str, str]]]) ->
> None:
>
> And this is the same function but with the parameters expanded
> into their traditional basic types.
>
> Without all the type hinting gubbins it would simply be:
>
> def broadcast_message(message, servers):
>  ....
>
> So all the detritus above is doing is attempting to make it
> clearer what the two parameters actually are in data terms.
> The first is a string, the second is a complex structure
> of nested tuples and a dict (which probably should all
> be wrapped in a class!).
>
> > I think this even more confusing. Can someone explain this in simple
> words?
> > I don't have a intense computer science background.
>
> Type hints are a way to specify the types of function parameters.
> They are an attempt to make complex type structures more readable
> rather than fixing the data to be simpler (which, to be fair,
> may not always be possible/easy). They are also an attempt to
> bring some of the "benefits" of static typing into Python but
> with very limited success. But they are only hints, you can
> happily survive without them.
>
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
>
>
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