using in try catch block

[David Anthoff]

I’m trying to use ``using`` in a try catch block, but that doesn’t seem to be supported.

 

Any other way around this? Essentially I want to load a package, and if the package is not installed, automatically do a ``Pkg.add``.

 

I could of course get a list of all the installed packages and see if the one I need is there, but given the slowness of the package manager, I would prefer to just try to load it first, and only if that fails attempt to ``Pkg.add``.

 

Thanks,

David

 

--

David Anthoff

University of California, Berkeley

 

http://www.david-anthoff.com

 

[Tom Breloff]

Here is what I use for this sort of logic:

function is_installed(pkgstr::AbstractString)

    try

        Pkg.installed(pkgstr) === nothing ? false: true

    catch

        false

    end

end

[Yichao Yu]

On Jun 27, 2016 12:20 PM, "Tom Breloff" <t...@breloff.com> wrote:
>
> Here is what I use for this sort of logic:
>
> function is_installed(pkgstr::AbstractString)
>     try
>         Pkg.installed(pkgstr) === nothing ? false: true

Dont do this since this will miss package in load path. Just eval a using expression.

[David Anthoff]

Perfect, that is exactly the kind of thing I was looking for! Thanks, David

[Tom Breloff]

Yichao: is there an alternative "is_installed" definition that would check the load path?  Lets assume I don't actually want to import it, just check.

[Yichao Yu]

On Jun 27, 2016 12:58 PM, "Tom Breloff" <t...@breloff.com> wrote:
>
> Yichao: is there an alternative "is_installed" definition that would check the load path?  Lets assume I don't actually want to import it, just check.

No.

[Cameron McBride]

On Mon, Jun 27, 2016 at 1:02 PM, Yichao Yu <yyc...@gmail.com> wrote:
>
> On Jun 27, 2016 12:58 PM, "Tom Breloff" <t...@breloff.com> wrote:
> >
> > Yichao: is there an alternative "is_installed" definition that would check the load path?  Lets assume I don't actually want to import it, just check.
>
> No.

Seems like potentially useful function for Pkg module?

Pkg.is_installed(pkgstr)

Or perhaps more useful: is_missing(...)

Although just having several Pkg.add(...) statements for a "setup" step also seems reasonable.

Cameron

[Yichao Yu]

On Mon, Jun 27, 2016 at 1:43 PM, Cameron McBride
<cameron...@gmail.com> wrote:
>
>
> On Mon, Jun 27, 2016 at 1:02 PM, Yichao Yu <yyc...@gmail.com> wrote:
>>
>> On Jun 27, 2016 12:58 PM, "Tom Breloff" <t...@breloff.com> wrote:
>> >
>> > Yichao: is there an alternative "is_installed" definition that would
>> > check the load path? Lets assume I don't actually want to import it, just
>> > check.
>>
>> No.
>
> Seems like potentially useful function for Pkg module?

https://github.com/JuliaLang/julia/issues/8679

[Jeffrey Sarnoff]

Re: Pkg.is_installed(_), Pkg.is_missing(_)

Pkg.has(_)

[Tony Kelman]

Be aware that doing this kind of thing in combination with precompilation is brittle and error prone (precompiled results will not match the actual status of available packages if that changes). Optional dependencies are better supported by moving code that depends on both other packages into its own package that can declare a dependency on both.