https://github.com/mlaloux/My-Python-GIS_StackExchange-answers/blob/master/How%20to%20add%20a%20column%20in%20QGIS%20via%20python.md

shpefile_add_field.py

from shapely.geometry import mapping, shape
import fiona
import csv

record_index = 'grid	filed1 filed2'

record_index = record_index.split()

all_record = {}

with open("resut.csv", 'r') as f:
    r = csv.DictReader(f)
    for i in r:
        all_record[i['\ufeffgrid']] = i

with fiona.collection('demo_area.shp', 'r') as polygon:
    schema = polygon.schema.copy()
    for i in record_index:
        if i != 'grid':
            schema['properties'][i] = 'int'
    schema['grid'] = 'str'

    with fiona.collection('test_area.shp', 'w', 'ESRI Shapefile', schema) as output:
        polygons = [elem for elem in polygon]

        for poly in polygons:
            res = {}
            ret_pro = {**poly['properties'], **all_record[poly['properties']['grid']]}
            del ret_pro['\ufeffgrid']
            res['properties'] = ret_pro

            res['geometry'] = mapping(shape(poly['geometry']))
            output.write(res)