Merge multiple GeoJSON files into one

merge-geojsons.py

from json import load, JSONEncoder
from optparse import OptionParser
from re import compile

float_pat = compile(r'^-?\d+\.\d+(e-?\d+)?$')
charfloat_pat = compile(r'^[\[,\,]-?\d+\.\d+(e-?\d+)?$')

parser = OptionParser(usage="""%prog [options]

Group multiple GeoJSON files into one output file.

Example:
  python %prog -p 2 input-1.json input-2.json output.json""")

defaults = dict(precision=6)

parser.set_defaults(**defaults)

parser.add_option('-p', '--precision', dest='precision',
                  type='int', help='Digits of precision, default %(precision)d.' % defaults)

if __name__ == '__main__':
    
    options, args = parser.parse_args()
    infiles, outfile = args[:-1], args[-1]

    outjson = dict(type='FeatureCollection', features=[])
    
    for infile in infiles:
        injson = load(open(infile))
        
        if injson.get('type', None) != 'FeatureCollection':
            raise Exception('Sorry, "%s" does not look like GeoJSON' % infile)
        
        if type(injson.get('features', None)) != list:
            raise Exception('Sorry, "%s" does not look like GeoJSON' % infile)
        
        outjson['features'] += injson['features']

    encoder = JSONEncoder(separators=(',', ':'))
    encoded = encoder.iterencode(outjson)
    
    format = '%.' + str(options.precision) + 'f'
    output = open(outfile, 'w')
    
    for token in encoded:
        if charfloat_pat.match(token):
            # in python 2.7, we see a character followed by a float literal
            output.write(token[0] + format % float(token[1:]))

        elif float_pat.match(token):
            # in python 2.6, we see a simple float literal
            output.write(format % float(token))

        else:
            output.write(token)

It would be better to specify for output file by a parameter instead of taking the last file as output because if someone forgets to give the output file then the last input file is replaced and hence the data it contained is lost.

@neogeomat

My fork solves that, defaults output to stdout. I have also updated the depcreated optparse to argparse.