Get all elementary flows generated by an activity in Brightway - brightway

Question

I would like to access to all elementary flows generated by an activity in Brightway in a table that would gather the flows and the amounts.
Let's assume a random activity :
lca=bw.LCA({random_act:2761,method)
lca.lci()
lca.lcia()
lca.inventory
I have tried several ways but none works :
I have tried to export my lci with brightway2-io but some errors appear that i cannot solve :
bw2io.export.excel.lci_matrices_to_excel(db_name) returns an error when computing the biosphere matrix data for a specific row :
--> 120 bm_sheet.write_number(bio_lookup[row] + 1, act_lookup[col] + 1, value)
122 COLUMNS = (
123 u"Index",
124 u"Name",
(...)
128 u"Location",
129 )
131 tech_sheet = workbook.add_worksheet("technosphere-labels")
KeyError: 1757
I try to get manually the amount of a specific elementary flow. For example, let's say I want to compute the total amount of Aluminium needed for the activity. To do so, i try this:
flow_Al=Database("biosphere3").search("Aluminium, in ground")
(I only want the resource Aluminium that is extracted as a ore, from the ground)
amount_Al=0
row = lca.biosphere_dict[flow_Al]
col_indices = lca.biosphere_matrix[row, :].tocoo()
amount_consumers_lca = [lca.inventory[row, index] for index in col_indices.col]
for j in amount_consumers_lca:
amount_Al=amount_Al+j
amount_Al`
This works but the final amount is too low and probably isn't what i'm looking for...
How can I solve this ?
Thank you

Answer 1

This will work on Brightway 2 and 2.5:
import pandas as pd
import bw2data as bd
import warnings
def create_inventory_dataframe(lca, cutoff=None):
array = lca.inventory.sum(axis=1)
if cutoff is not None and not (0 < cutoff < 1):
warnings.warn(f"Ignoring invalid cutoff value {cutoff}")
cutoff = None
total = array.sum()
include = lambda x: abs(x / total) >= cutoff if cutoff is not None else True
if hasattr(lca, 'dicts'):
mapping = lca.dicts.biosphere
else:
mapping = lca.biosphere_dict
data = []
for key, row in mapping.items():
amount = array[row, 0]
if include(amount):
data.append((bd.get_activity(key), row, amount))
data.sort(key=lambda x: abs(x[2]))
return pd.DataFrame([{
'row_index': row,
'amount': amount,
'name': flow.get('name'),
'unit': flow.get('unit'),
'categories': str(flow.get('categories'))
} for flow, row, amount in data
])
The cutoff doesn't make sense for the inventory database, but it can be adapted for the LCIA result (characterized_inventory) as well.
Once you have a pandas DataFrame you can filter or export easily.