AttributeError "'int' object has no attribute 'encode'" when writing GeoDataFrame into shapefile or spatialite with GeoPandas

Question

I am trying to save a GeoDataFrame as a shapefile or spatialite, but for some reason, I get this error:

File "fiona\ogrext.pyx", line 951, in fiona.ogrext.WritingSession.start (fiona/ogrext.c:16479) AttributeError: 'int' object has no attribute 'encode'

My GeoDataFrame appears correctly without any issues, look's like there is something wrong with my gdf.to_file command, but I have no idea what.

I checked if I have the most up-to-date libraries.

This is the code I use:

def writeIntoDatabase(input_path, numpy_point_array, 30):
    
    print ('Reading data into shp')
    df = pd.DataFrame(numpy_point_array)
    dfthresh = df.loc[df[3] < 30]
    geometry = [Point(xyz) for xyz in zip(dfthresh[0], dfthresh[1], dfthresh[2])]
    #df = df.drop(['Lon', 'Lat', 'Alt'], axis=1)

    print(geometry)    

    crs = {'init': 'epsg:27700'}

    gdf = GeoDataFrame(dfthresh, crs=crs, geometry = geometry)
    print (gdf)

    gdf.to_file(driver = 'ESRI Shapefile', filename = input_path)

Can you help me?

Answer 1

As I don't know your data, I give you a solution with my data (with x,y, z and a colum to test < 30). If I use your solution

import geopandas as gpd
import numpy as np
import pandas as pd
numpy_point_array = np.array([[202104.271187,90516.656257,170.520004272, 45],[202139.659561,90516.656257,170.740005493, 15],[202175.047935,90516.656257,170.809997559, 12],[202210.436309,90516.656257,170.75, 10],[202245.824683,90516.656257,170.13999939, 31]])
df = pd.DataFrame(numpy_point_array)
dfthresh = df.loc[df[3] < 30]
from shapely.geometry import Point
geometry = [Point(xyz) for xyz in zip(dfthresh[0], dfthresh[1], dfthresh[2])]
import geopandas as gpd
crs = {'init': 'epsg:27700'}
gdf = gpd.GeoDataFrame(dfthresh, crs=crs, geometry = geometry)

The name of the columns are

list(gdf)
[0, 1, 2, 3, 'geometry'] 

And a shapefile does not accept integers as column names -> Fiona error AttributeError: 'int' object has no attribute 'encode'

The solution ?, give a name to the fields when you create a DataFrame

# creation of a DataFrame with string column names
df = pd.DataFrame(numpy_point_array, columns=['x','y','z','test'])
df.head()
         x             y           z        test
0  202104.271187  90516.656257  170.520004  45.0
1  202139.659561  90516.656257  170.740005  15.0
2  202175.047935  90516.656257  170.809998  12.0
3  202210.436309  90516.656257  170.750000  10.0
4  202245.824683  90516.656257  170.139999  31.0

And you can simplify your script

# selection
df =  df[df['test'] < 30]
df.head()
           x             y           z      test
1  202139.659561  90516.656257  170.740005  15.0
2  202175.047935  90516.656257  170.809998  12.0
3  202210.436309  90516.656257  170.750000  10.0
# convert to GeoDataFrame
# create a geometry column from the dataFrame x,y,z columns
df['geometry'] = df.apply(lambda row: Point(row.x,row.y,row.z),axis=1)
df = df.drop(['x', 'y', 'z'], axis=1)
# create the GeoDatFrame
gdf = gpd.GeoDatFrame(df, geometry = df.geometry)
# save the GeoDataFrame
gdf.to_file(driver = 'ESRI Shapefile', filename= "result.shp")
# or directly
gdf.to_file("result2.shp")