Decode a Factorio blueprint string, change some of it and reencode it

factorio_blueprint_string_edit.py

import json
import zlib
import base64

original_bp_string = '0eNp9j80OgjAQhN9lzq0RFNC+ijGGnw1uQhdCi5GQvrstXjx5m9mfb2c3NMNC08ziYTZwO4qDuW1w3Es9pJpfJ4IBe7JQkNomVztHthlYem3r9slCOkdQYOnoDZOFuwKJZ8/05e1mfchiG5rjwH+SwjS6uDxKShCB+nQoFNYoskOR7sQ0LvWmeeyW1vMr0rWNeiB9gslDSrBnNj8vKrxodjs2v2Tn6nytyio7lkUZwgd0Blhx'
bp_json = json.loads(zlib.decompress(base64.b64decode(original_bp_string[1:])).decode('utf8'))

# there is one entity in the blueprint, it's an assembler with a item request for 2 prod-3 modules and no recipe set
# for the fields of the blueprint json see https://wiki.factorio.com/Blueprint_string_format
bp_json['blueprint']['entities'][0]['items'] = {'copper-plate': 200} # overwrites existing item request
bp_json['blueprint']['entities'][0]['recipe'] = 'copper-cable' # creates new key/value pair


changed_bp_string = '0' + base64.b64encode(zlib.compress(bytes(json.dumps(bp_json), 'utf8'))).decode('utf8')
print(changed_bp_string)