ZeroDivisionError: division by zero

[naoren]

Hello, thank you for your wonderful project. There were some problems when I tried to apply code on a polymer dataset using --motif command. Is this the problem of my SMILES strings, or other possible problems, and how should I solve it?

Graph contraction status: True
Start grammar evaluation...
Generating sample 0/100
Traceback (most recent call last):
File "main.py", line 211, in
learn(mol_sml, args)
File "main.py", line 130, in learn
eval_metric = evaluate(l_grammar, args, metrics=['diversity', 'syn'])
File "main.py", line 33, in evaluate
mol, iter_num = random_produce(grammar)
File "D:\D_E_G\grammar_generation.py", line 162, in random_produce
_, idx = sample(starting_rules)
File "D:\D_E_G\grammar_generation.py", line 139, in sample
prob = [1/len(l)] * len(l)
ZeroDivisionError: division by zero