[QGIS-Developer] [Qgis-user] Question About QgsGeometry Static Functions

C Hamilton adenaculture at gmail.com
Thu Dec 6 07:02:59 PST 2018


Thanks Nyall. I think I had a misunderstanding in that the XY routines were
the preferred method to use unless you have Z/M dimensions. I will look at
changing my code.

Calvin

On Wed, Dec 5, 2018 at 6:06 PM Nyall Dawson <nyall.dawson at gmail.com> wrote:

> On Wed, 5 Dec 2018 at 02:52, C Hamilton <adenaculture at gmail.com> wrote:
> >
> > QgsGeometry has the following static functions
> >
> > QgsGeometry.fromPolylineXY( list of QgsPointXY)
> > QgsGeometry.fromMultiPolylineXY( list of QgsPointXY lists)
> >
> > If I am working with QgsPoint rather than QgsPointXY there is
> >
> > QgsGeometry.fromPolyline( list of QgsPoint)
> >
> > However there is not a similar multi polyline function. Why not?
>
> Because there's been no demand for this, until now. But in general all
> those fromPolylineXY etc methods should be avoided wherever possible.
> They are very slow (lots of list allocations) and don't handle Z/M
> dimensions.
>
> You're better to work directly with the QGIS geometry subclasses like
> QgsLineString, QgsMultiLineString instead.
>
> Nyall
>
>
> >
> > QgsGeometry.fromMultiPolyline( list of QgsPoint list)
> >
> > What is the proper way to implement this?
> >
> > Thanks!!!!
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