2

This is what I'm trying to run:

import sys, glob

# Prepare the environment
from qgis.core import * # qgis.core must be imported before PyQt4.QtGui!!!
from PyQt4.QtGui import *
app = QApplication([])
QgsApplication.setPrefixPath("/usr/bin/qgis", True) # The True value is important
QgsApplication.initQgis()

# Prepare processing framework 
from processing.core.Processing import Processing
Processing.initialize()
from processing.tools import *

from osgeo import ogr
driver = ogr.GetDriverByName('ESRI Shapefile')
driver2 = ogr.GetDriverByName('ESRI Shapefile')
dataSource = driver.Open("file1.shp", 1) #1 is read/write
dataSource2 = driver.Open("file2.shp", 1) #1 is read/write
layer1 = dataSource.GetLayer()
layer2 = dataSource.GetLayer()

Processing.runAlgorithm("qgis:mergevectorlayers", layer1, layer2, '/home/name/Desktop/output.shp')

But I get this error:

[Finished in 0.2s with exit code 1]
[shell_cmd: python -u "/home/none/Desktop/testattribute/merged.py"]
[dir: /home/name/Desktop/testattribute]
[path: /home/name/torch/install/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games]

I'm using Processing 2.12.2.

Now I'm running this code from @gene with the addition that I'm trying to use it in a loop that iterates through a list of shapefiles:

meta = fiona.open(filelist[0]).meta
    for shapefile in filelist:
        with fiona.open(exportname, 'w', **meta) as output:
            for features in fiona.open(shapefile):
                output.write(features)

But I do not end up with a valid shapefile. What am I doing wrong?

I ended up sorting it out into a somewhat hacked looking script.

def mergeshp(firstshp, secondshp, index):
    exportname = 'mergeshp_' + str(index) + '.shp'
    meta = fiona.open(firstshp).meta
    with fiona.open(exportname , 'w', **meta) as output:
       for features in fiona.open(firstshp):
           output.write(features)
       for features in fiona.open(secondshp):
           output.write(features)
    return exportname

And I called it with this code:

numfiles = len(shapelist)

i=0
mergedshp = mergeshp(shapelist[i],shapelist[i+1], i)
i += 2
while i<numfiles:
    mergedshp = mergeshp(mergedshp, shapelist[i], i)
    i += 1
PolyGeo
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Jas
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1 Answers1

7

Instead of using PyQGIS from outside why not use directly Python without QGIS if you want to merge shapefiles ?

1) You can use PyShp (shapefiles) as in Merging Lots of Shapefiles (quickly)
2) You can use osgeo/ogr as in Python: shapefile merger utility
3) You can use Fiona

a) If the schema of the shapefiles are the same:

import fiona
meta = fiona.open('shapefile_one.shp').meta
with fiona.open('merge.shp', 'w', **meta) as output:
   for features in fiona.open("shapefile_one.shp"):
       output.write(features)
   for features in fiona.open("shapefile_two.shp"):
       output.write(features)
   ...

You can simplify this script with an original list of shapefiles

b) If the schema of the shapefiles are different:

Simply merge the schemas of the shapefiles

gene
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  • Thanks for your response. While it worked great as you wrote it when I tried to wrap it in a loop to iterate through a list of shapefiles I end up with an invalid shapefile at the end. I think it's my lack of understanding of the .meta or meta. meta = fiona.open(filelist[0]).meta for shapefile in filelist: with fiona.open(exportname, 'w', meta) as output: for features in fiona.open(shapefile): output.write(features) – Jas Mar 06 '16 at 21:42
  • I think you could easily answer this other question I have as well. I'm trying to use fiona there also but unfortunately what I'm trying to do seems to simple for anyone to bother giving an example of how to do it outside of QGIS or arcpy. – Jas Mar 07 '16 at 03:16
  • 1
    Done in the other question – gene Mar 08 '16 at 09:47