def _hash_filter_fn(self, filter_fn, **kwargs):
""" Construct string representing state of filter_fn
Used to cache filtered variants or effects uniquely depending on filter fn values
"""
filter_fn_name = self._get_function_name(filter_fn, default="filter-none")
logger.debug("Computing hash for filter_fn: {} with kwargs {}".format(filter_fn_name, str(dict(**kwargs))))
# hash function source code
fn_source = str(dill.source.getsource(filter_fn))
pickled_fn_source = pickle.dumps(fn_source) ## encode as byte string
hashed_fn_source = int(hashlib.sha1(pickled_fn_source).hexdigest(), 16) % (10 ** 11)
# hash kwarg values
kw_dict = dict(**kwargs)
kw_hash = list()
if not kw_dict:
kw_hash = ["default"]
else:
[kw_hash.append("{}-{}".format(key, h)) for (key, h) in sorted(kw_dict.items())]
# hash closure vars - for case where filter_fn is defined within closure of filter_fn
closure = []
nonlocals = inspect.getclosurevars(filter_fn).nonlocals
for (key, val) in nonlocals.items():
## capture hash for any function within closure
if inspect.isfunction(val):
closure.append(self._hash_filter_fn(val))
closure.sort() # Sorted for file name consistency
closure_str = "null" if len(closure) == 0 else "-".join(closure)
# construct final string comprising hashed components
hashed_fn = ".".join(["-".join([filter_fn_name,
str(hashed_fn_source)]),
".".join(kw_hash),
closure_str]
)
return hashed_fn
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