Is there a more Pythonic way of doing this?:
if self.name2info[name]['prereqs'] is None:
self.name2info[name]['prereqs'] = []
if self.name2info[name]['optionals'] is None:
self.name2info[name]['optionals'] = []
The reason I do this is because I need to iterate over those later. They're None to begin with sometimes because that's the default value. It's my workaround to not making [] a default value.
Thanks.
If you prefer this:
self.name2info[name]['prereqs'] = self.name2info[name]['prereqs'] or []
You could do it this way:
if not self.name2info[name]['prereqs']: self.name2info[name]['prereqs'] = []
or this way
self.name2info[name]['prereqs'] = [] if not self.name2info[name]['prereqs'] else self.name2info[name]['prereqs']
If you can't fix the input you could do this (becomes 'better' if you need to add more):
for prop in ['prereqs', 'optionals']:
if self.name2info[name][prop] is None:
self.name2info[name][prop] = []
But replacing these values to be iterating over the empty list you just added doesn't make a whole lot of sense (unless maybe if you're appending something to this list at some point). So maybe you could just move the test for None-ness right before the iteration:
prereqs = self.name2info[name]['prereqs']
if prereqs is not None:
for prereq in prereqs:
do_stuff(prereq)
Slightly going off-topic now, but if you ever want to test if an item is iterable at all, a common (pythonic) way would be to write:
try:
my_iterable_obj = iter(my_obj)
except TypeError:
# not iterable
Every one of those attribute and dict lookups takes time and processing. It's Pythonic to look up self.name2info[name] just once, and then work with a temporary name bound to that dict:
rec = self.name2info[name]
for key in "prereqs optionals required elective distance".split():
if key not in rec or rec[key] is None:
rec[key] = []
Now if need to add another category, like "AP_credit", you just add that to the string of key names.