Useful code snippets to Clip polygon with another polygon and Convert Vector file in Geopackage to Shapefile in QGIS

 Clip polygon with another polygon using processing algorithm in QGIS

# Clip polygon with another polygon using processing algorithm in QGIS

ovly = 'C:\\Users\\Yusuf_08039508010\\Desktop\\Working_Files\\...\\Name_Bouganville Lower - N.gpkg'

outfile = ovly.split('\\')[-1].replace('Name_', '').replace('.gpkg', '')
print('Processing...', outfile)

parameters = {'INPUT':'C:\\Users\\Yusuf_08039508010\\Desktop\\Working_Files\\...\\Results\\SHP\\Woody_02.shp',
'OVERLAY':ovly,
'OUTPUT':f'C:/Users/Yusuf_08039508010/Desktop/Working_Files/.../Results/SHP/Study Location Individual Files/SHP with Holes/{outfile}.shp'}

processing.run("native:clip", parameters)



# -----------------------------------------------
# Bulk Clip polygon with another polygon using processing algorithm in QGIS

import glob

overlay_file = glob.glob('C:\\Users\\Yusuf_08039508010\\Desktop\\Working_Files\\Fiverr\\2022\\06-June\\Masking None Vegetation Ground Covers\\Results\\SHP\\Study Location Individual Files\\*.gpkg')

failed = []
for ovly in overlay_file:
    try:
        outfile = ovly.split('\\')[-1].replace('Name_', '').replace('.gpkg', '')
        print('Processing...', outfile)

        parameters = {'INPUT':'C:\\Users\\Yusuf_08039508010\\Desktop\\Working_Files\\Fiverr\\2022\\06-June\\Masking None Vegetation Ground Covers\\Results\\SHP\\Woody_02.shp',
        'OVERLAY':ovly,
        'OUTPUT':f'C:/Users/Yusuf_08039508010/Desktop/Working_Files/Fiverr/2022/06-June/Masking None Vegetation Ground Covers/Results/SHP/Study Location Individual Files/SHP with Holes/{outfile}.shp'}

        processing.run("native:clip", parameters)
    except Exception:
        failed.append(ovly)

print('Done...')

Convert Vector file in Geopackage to Shapefile

# Convert Vector file in Geopackage to Shapefile


gpkg = 'C:\\Users\\Yusuf_08039508010\\Desktop\\Working_Files\\...\\Name_Bouganville Lower - N.gpkg'

# Read vector layer and test it is valid....
input_file = QgsVectorLayer(gpkg, "polygon", "ogr")
input_file.isValid()

# Construct output file name...
out_filename = gpkg.split('\\')[-1].replace('.gpkg', '')

# Write the file to disc...
out_folder = r"C:\Users\Yusuf_08039508010\Desktop\Working_Files\...\Results\SHP\Study Location Individual Files\Failed files"
QgsVectorFileWriter.writeAsVectorFormat(input_file, f"{out_folder}\\{out_filename}.shp", "UTF-8", input_file.crs(), "ESRI Shapefile")

print('Done...')

# -----------------------------------------------------------


# Bulk Convert Vector file in Geopackage to Shapefile
import glob

gpkg_folder = r"C:\Users\Yusuf_08039508010\Desktop\Working_Files\Fiverr\2022\06-June\Masking None Vegetation Ground Covers\Results\Deliverables\Shp\gpk"

gpkg_files = glob.glob(f'{gpkg_folder}\\*.gpkg')

for gpkg in gpkg_files:
    # Read vector layer and test it is valid....
    input_file = QgsVectorLayer(gpkg, "polygon", "ogr")
    input_file.isValid()
    
    # Construct output file name...
    out_filename = gpkg.split('\\')[-1].split('_')[-1].replace('.gpkg', '')

    # Write the file to disc...
    out_folder = r"C:\Users\Yusuf_08039508010\Desktop\Working_Files\Fiverr\2022\06-June\Masking None Vegetation Ground Covers\Results\Deliverables\Shp"
    QgsVectorFileWriter.writeAsVectorFormat(input_file, f"{out_folder}\\{out_filename}.shp", "UTF-8", input_file.crs(), "ESRI Shapefile")

print('Done...')

Different ways to read map layers into pyqgis

#1 - Read active layer from the layer panel
layer = iface.activeLayer() # or
layer = qgis.utils.iface.activeLayer()

  
#2 - Read all layers listed on the layers panel...
layers_on_panel = QgsProject.instance().mapLayers()


#3 - Read layer by name from the layer panel...
layer = QgsProject.instance().mapLayersByName('Churches')


#4 - Read from file...
vector_file = r"C:\Users\Yusuf_08039508010\Desktop\...\NGA_adm2.shp"
layer = QgsVectorLayer(vector_file, 'DISPLAYNAME', 'ogr')

Save all shapefile layer listed on the layer panel into a new directory/folder

# Save layers on layer panel to new folder...
import shutil

newFolder = r'C:\Users\Yusuf_08039508010\Desktop\Map of StudyArea\BMC SHP'

# Read all layers listed on the layers panel...
layers_on_panel = QgsProject.instance().mapLayers()

# Loop over each file and copy it to new folder location...
for k, v in layers_on_panel.items():
    # Construct file name...
    fn = v.name() + '.shp'
    
    # Get file path...
    fp1 = v.source()
    fp2 = v.source().replace('.shp', '') + '.dbf'
    fp3 = v.source().replace('.shp', '') + '.shx'
    fp4 = v.source().replace('.shp', '') + '.prj'
    fp5 = v.source().replace('.shp', '') + '.prj'
    
    print('Copying....', fn)
    print('')
    
    # Copy the shapefiles to new folder location...
    shutil.copy( fp1, newFolder ) # shutil.copy( src, dst )
    shutil.copy( fp2, newFolder )
    shutil.copy( fp3, newFolder )
    shutil.copy( fp4, newFolder )
    shutil.copy( fp5, newFolder )
    
    # break

print('Done...')