1

I'm trying to load a shapefile into QGIS using iface.addVectorLayer, but whenever I do this, I get an error message "Layer is not valid: etc ..."

However, if I try to load the same shapefile use the menu dialog "Add Vector Layer", it loads fine. I have loaded raster files, so I know it's not some funny with the path name.

I'm sure I'm missing something obvious here, but what?

enter image description here

This line works:-

layer1 = iface.addRasterLayer("H:\Mapping Stuff\NE1_50M_SR_W\NE1_50M_SR_W\NE1_50M_SR_W.tif", "basemap")

This doesn't:-

layer2 = iface.addVectorLayer("H:\Mapping Stuff\ne_50m_urban_areas\ne_50m_urban_areas.shp", "urban", "ogr")
Improve this question
9
  • Please post your code.
    – underdark
    Commented Jun 1, 2015 at 17:42
  • Can you post your code (only the piece that loads the shp)
    – luca76
    Commented Jun 2, 2015 at 6:49
  • Are you 100% sure your vector file path is right? I just test it with no problems on my machine.
    – Germán Carrillo
    Commented Jun 2, 2015 at 14:42
  • 1
    @gcarrillo - I also received the same error message as the OP if only single slashes are used for shapefiles instead of double. Perhaps a platform issue as I use Windows?
    – Joseph
    Commented Jun 2, 2015 at 15:02
  • @gcarrillo - Yes, it's correct; here is the path copied using "Copy as Path" :-"H:\Mapping Stuff\ne_50m_urban_areas\ne_50m_urban_areas.shp"
    – LeighM
    Commented Jun 2, 2015 at 15:05

3 Answers 3

Reset to default
1

QGis likes path to be using forward slash, like on Unix system. So, if you change all of the backslashes to forward slash then it will work on your windows box.

Improve this answer
0

Try this (note the double slashes for the directory in which your shapefile resides in):

layer2 = iface.addVectorLayer("H:\Mapping Stuff\ne_50m_urban_areas\\ne_50m_urban_areas.shp", "urban", "ogr")
Improve this answer
4
  • Not completely sure why a single slash works for rasters and not for vectors, perhaps someone can enlighten us with this =)
    – Joseph
    Commented Jun 2, 2015 at 14:22
  • 2
    Joseph's solution of placing double slashes in front of filename (\\ne_50m_urban_areas.shp) works for me. After many attempts, none of the previous suggestions did.
    – J. Browne
    Commented Dec 15, 2016 at 3:17
  • I had the same problem. Rasterfiles worked with normal slashes ("/") in the path but loading shapefiles did not. I just replaced the last "/" of a path right before the actual filename by "\\" and now it works. Could anybody clarify why this is the case? I am working with QGIS 3.8
    – philsch
    Commented Nov 13, 2019 at 13:28
  • 1
    @philsch - Might be better if you ask this as a new question and mention what platform you are using and include a reference to this question to show you did some research but you're asking why this happens. I use Windows and had problems using the single forward slash.
    – Joseph
    Commented Nov 13, 2019 at 13:56
0

In C and C++, and as far as I know also Python, backslashes are used to identify special characters. For instance,

'\t' = TAB character

'\n'= New Line

Pay attention: lowercase; this might explain why one of your strings does not work. In order to inform the compiler (interpreter) that we want an actual backslash inside of a string, we must type two backslashes:

'\\'

Windows accepts both separators, \ and /, so in principle it should be ok to use "h:/blabla".

By the way, this is an old trick that ages back to Pascal; in that language, quotes can be inserted in a string by duplication, eg. "Here are some ""quotes"" !".

In C/C++ (?Python?), the equivalent is "Here are some \"quotes\" !"

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.