Setting all inputs of an activity to 0 in wurst and brightway - brightway

Question

Trying to set the existing exchanges (inputs) of an activity to zero and additionally adding an exchange, the following is returned:
"MultipleResults("Multiple production exchanges found")"
"NoResults: No suitable production exchanges founds"
Firstly I set all the input amounts to zero except for the output:
for idx, item in enumerate(ds['exchanges']):
item['amount'] = 0
ds['exchanges'][0]['amount'] = 1
Secondly, I add the a new exchange:
ds['exchanges'].append({
'amount': 1,
'input': (new['database'], new['code']),
'type': 'technosphere',
'name': new['name'],
'location': new['location']
})
Writing the database in the last steps returns the errors.
w.write_brightway2_database(DB, NEW_DB_NAME)
Does anyone see where the problem could be or if there are alternative ways to replace multiple inputs with another one?
Thanks a lot for any hints!
Lukas
Full error traceback:
--------------------------------------------------------------------------
NoResults Traceback (most recent call last)
<ipython-input-6-d4f2dde2b33d> in <module>
2
3 NEW_DB_NAME = "ecoinvent_copy_new"
----> 4 w.write_brightway2_database(ecoinvent, NEW_DB_NAME)
5
6 # Check for new databases
~\Miniconda3\envs\ab\lib\site-packages\wurst\brightway\write_database.py in write_brightway2_database(data, name)
47
48 change_db_name(data, name)
---> 49 link_internal(data)
50 check_internal_linking(data)
51 check_duplicate_codes(data)
~\Miniconda3\envs\ab\lib\site-packages\wurst\linking.py in link_internal(data, fields)
11 input_databases = get_input_databases(data)
12 get_tuple = lambda exc: tuple([exc[f] for f in fields])
---> 13 products = {
14 get_tuple(reference_product(ds)): (ds['database'], ds['code'])
15 for ds in data
~\Miniconda3\envs\ab\lib\site-packages\wurst\linking.py in <dictcomp>(.0)
12 get_tuple = lambda exc: tuple([exc[f] for f in fields])
13 products = {
---> 14 get_tuple(reference_product(ds)): (ds['database'], ds['code'])
15 for ds in data
16 }
~\Miniconda3\envs\ab\lib\site-packages\wurst\searching.py in reference_product(ds)
82 and exc['type'] == 'production']
83 if not excs:
---> 84 raise NoResults("No suitable production exchanges founds")
85 elif len(excs) > 1:
86 raise MultipleResults("Multiple production exchanges found")
NoResults: No suitable production exchanges found

Answer 1

It seems that setting the exchanges to zero caused the problem. The database cannot be written in this case. What I did now is setting the exchanges to a very small number, so that they have no effect on the impact assessment, but are not zero. Not the most elegant way, but works for me. So if anyone has similar problems, that might be a quick solution.