Conduct Buffer Analysis in PyQGIS

Question

• Given that I have 1 shapefiles for instance c:/users/user/line.shp

• and I have activated my QGIS Console in Anaconda prompt

(base) $ conda activate qgis-venv
(qgis-venv) $ python

>>> import qgis
>>> #????

• How should I put command in the console to execute buffer of 500?

Answer 1

You can try this :

import sys
from qgis.core import (
     QgsApplication, 
     QgsProcessingFeedback, 
     QgsVectorLayer
)

# See https://gis.stackexchange.com/a/155852/4972 for details about the prefix 
QgsApplication.setPrefixPath('/usr', True)
qgs = QgsApplication([], False)
qgs.initQgis()

# Append the path where processing plugin can be found
sys.path.append('/docs/dev/qgis/build/output/python/plugins')

import processing
from processing.core.Processing import Processing
Processing.initialize()

vlayer = QgsVectorLayer('P:/Test/qgis_test/poly_test.shp', "poly_test", "ogr")

parameter_dictionary = {
    'INPUT' : vlayer,
    'DISTANCE' : 500,
    'SEGMENTS' : 25,
    'END_CAP_STYLE' : 0,
    'JOIN_STYLE' : 1,
    'MITER_LIMIT' : 10,
    'DISSOLVE' : False,
    'OUTPUT' : 'memory:'
    }

buffer_result = processing.run("native:buffer", parameter_dictionary)

output = buffer_result['OUTPUT']

Also do not forget to check the QGIS Documentation

---

References:

• Using QGIS 3 Processing algorithms from PyQGIS standalone scripts (outside of GUI)
• Buffering in PyQGIS

Answer 2

# YOU CAN ADJUST THIS with your file paths and country UTM
import geopandas as gpd

# Load the shapefile
hospitals = gpd.read_file(r'C:\GIS\GIS_2024\GIS_Spartial_Analysis\ShapeFile\hSites.shp')

# Reproject to UTM Zone 35S (EPSG:32735)
hospitals_utm = hospitals.to_crs(epsg=32735)

# Create a 5KM buffer
hospitals_utm['geometry'] = hospitals_utm.buffer(5000)  # 5000 meters

# Save the output to a new shapefile
output_path = r'C:\GIS\GIS_2024\GIS_Spartial_Analysis\Buffer_001\Buffer_5km.shp'
hospitals_utm.to_file(output_path)