Remove all instances of mutable objects (e.g. empty lists or dictionaries) as default parameter values

[dchristidis]

Motivation

Read Python Mutable Defaults Are The Source of All Evil. The likelihood of this anti-pattern is low, but given the magnitude, it might be worth removing all such instances.

Modification

Identify all instances with pylint --disable=all --enable=W0102 lib/rucio/. Use None as default value, but add type hints and initialise the parameter in the body. For example:

rucio/lib/rucio/core/rule.py

Line 735 in d19db9e

def list_rules(filters={}, session=None):

Should become:

@stream_session
def list_rules(filters: Optional[Dict] = None, session: Session = None) -> Iterable[Dict]:
    …
    filters = filters or {}
    …

[chinmaym07]

Hey Can I work on this ?

[bari12]

Hi @chinmaym07 yes, please go ahead. I would suggest to go module by module, starting with the ones in https://github.com/rucio/rucio/tree/master/lib/rucio/core