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After a few comments and my own consideration I've completely Edited the content (and title) of this post.

What are valid "output_layer" parameter options when scripting with the "saveselectedfeatures" tool?

I'm writing a script that uses the tool as follows:

processing.runandload('qgis:saveselectedfeatures', Input, 'Output.shp')

I also tried removing the shapefile extension and just putting 'Output' as the final parameter. Still errors and no resulting output.

Don't worry about "Input", it's a perfectly valid layer with selected features.

PARTIAL SOLUTION

@Joseph provided the partial solution of replacing " 'Output.shp' " with " None " (no quotations). 

processing.runandload('qgis:saveselectedfeatures', Input, None)

This results in successful execution with a temporary output layer called "Solution" popping up in the Layers Window.

BUT...

I call this a partial solution because I find it hard to believe that the designer(s) of this tool didn't also intend to give users the option to choose the name of their output file (as I originally tried to do) via the final parameter ('output_layer'), as described in the tool's Help Tab.

FINAL THOUGHTS

The tool's Help tab offers the following instruction:

enter image description here

enter image description here

But it seems this is not quite as "helpful" as it could be. It seems like a few short and simple examples of acceptable values for the 2nd parameter would avoid any confusion.

Something like:

Output file options:  temporary layer, Shapefile, etc...

2nd Parameter ('output_layer') options:  
" 'User_chosen_name' " (or " 'User_chosen_name.shp' "), OR "None" (produces auto-named temporary layer).

I'm a relatively new user of QGIS.

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  • As an FYI, you can replace runalg with runandload to load the output shapefile into QGIS.
    – Joseph
    Commented Oct 30, 2015 at 10:37
  • @user3309182 - Most welcome buddy :)
    – Joseph
    Commented Oct 30, 2015 at 11:49
  • Thanks @Joseph. A great tip to know! I'm using "runandload" now but nothing is loading. Obviously something is still wrong with one of my two parameters.
    – Waterman
    Commented Oct 30, 2015 at 11:51
  • @user3309182 - Could you edit your question please to include your script so that potential answerers have a better chance of helping you? :)
    – Joseph
    Commented Oct 30, 2015 at 11:58
  • @Joseph - Complete code now added but figured that would be distracting to the question since I'm quite confident it has no bearing on why "saveselectedfeatures" is failing. Reasoning: I know the first parameter is fine since "Input" is understood by another tool in my script. That leaves just the 2nd parameter where I figure the problem must be. Does that make sense?
    – Waterman
    Commented Oct 30, 2015 at 12:03

1 Answer 1

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Turns out (on a Mac at least) you have to put the full path plus the name for your file. For example, the following code places the output shapefile "MyFile" on my desktop. 

path = "/Users/User1/Desktop/"
processing.runandload('qgis:saveselectedfeatures', Input, path+'MyFile.shp')

Seems obvious in hindsight but again better documentation in the Help tab would have been a simple way to avoid confusion.

Still need to figure out why the output gets loaded onto map project as "Selection" and not with the name I provided ("MyFile"), but I've already asked that question in another post ("How to write QGIS script to load Output file to Map Project with Desired Name?")

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