1

I'm trying to develop a plugin in QGIS.

My issue is that I don't know how to transform an attribute table into a dataframe in order to use it further in run(self) function later.

I also used a comboBox in order to insert a layer the code below is located in run function:

layers=QgsProject.instance().layerTreeRoot().children()
self.dlg.comboBox.clear()
self.dlg.lineEdit.clear()
self.dlg.comboBox.addItems([layer.name() for layer in layers])
selectedLayerIndex=self.dlg.comboBox.currentIndex()
selectedLayer=layers[selectedLayerIndex].layer()

I used Plugin Builder and Qt Designer.

3

You can try:

import pandas as pd
lyr = QgsProject.instance().mapLayersByName('ok_ak_riks')[0]

#List all columns you want to include in the dataframe. I include all with:
cols = [f.name() for f in lyr.fields()] #Or list them manually: ['kommunnamn', 'kkod', ... ]

#A generator to yield one row at a time
datagen = ([f[col] for col in cols] for f in lyr.getFeatures())

df = pd.DataFrame.from_records(data=datagen, columns=cols)

enter image description here

2

You may use the following code to make the conversion. I make a conversion to a pandas DataFrame and then to a geopandas GeoDataFrame. You may use only first part of the recipe

You can also note that I do not cast each column to pandas dtype completely at the end of the script e.g https://stackoverflow.com/questions/21197774/assign-pandas-dataframe-column-dtypes. To get QGIS column types (human readable), look at unused columns_types in the code. The code to convert from Dataframe to GeoDataFrame is mainly borrowed from official GeoPandas doc section about Creating a GeoDataFrame from WKT format

import pandas as pd
import geopandas
from shapely import wkt

layer = layers[selectedLayerIndex].layer()
# for standalone case, comment above and uncomment below
# layer = iface.activeLayer()

columns = [f.name() for f in layer.fields()] + ['geometry']
columns_types = [f.typeName() for f in layer.fields()] # We exclude the geometry. Human readable
# or
# columns_types = [f.type() for f in layer.fields()] # QVariant type
row_list = []
for f in layer.getFeatures():
    row_list.append(dict(zip(columns, f.attributes() + [f.geometry().asWkt()])))

df = pd.DataFrame(row_list, columns=columns)
df['geometry'] = geopandas.GeoSeries.from_wkt(df['geometry'])
gdf = geopandas.GeoDataFrame(df, geometry='geometry')
gdf = gdf.set_crs(crs=layer.crs().toWkt())
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