Get the Unit Groups

[dt-woods]

For the openLCA JSON export, we need to create the unit groups that are associated with the flow units. openLCA has a standard convention for this, but not easy to access (e.g., it isn't completely documented in their olca-schema package, just the names and UUIDs).

For simplicity, consider using the unit groups that are defined on the Federal Elementary Flow List, which are in reference to GreenDelta's unit groups.
Here's how.

import io
import json
import os
from zipfile import ZipFile

import olca_schema as o
import requests

u_files = []
my_url = (
    "https://www.lcacommons.gov/"
    "lca-collaboration/ws/public/download/json/"
    "repository_Federal_LCA_Commons@elementary_flow_list")
r = requests.get(my_url, stream=True)
with ZipFile(io.BytesIO(r.content)) as zippy:
    # Find the unit groups, convert them to UnitGroup class
    for name in zippy.namelist():
        # Note there are only three folders:
        # 'flow_properties', 'flows', and 'unit_groups'; 
        # we want the 27 unit groups
        if name.startswith("unit") and name.endswith("json"):
            u_dict = json.loads(zippy.read(name))
            u_obj = o.UnitGroup.from_dict(u_dict)
            u_files.append(u_obj)

[dt-woods]

To archive the unit groups for future use, try the following after the above:

out_file = "unit_groups.json"
out_str = ",".join([json.dumps(x.to_dict()) for x in u_files])
out_str = "[%s]" % out_str
with open(out_file, 'w') as f:
    f.write(out_str)

[dt-woods]

and, if you are so inclined to test that this works, try this:

# Test that output file is good. YES!
with open(out_file, 'r') as f:
    my_list = json.load(f)

u_objs = []
for my_item in my_list:
    u_objs.append(o.UnitGroup.from_dict(my_item))