dict views can perform quick "is subset" testing via the inequality operators. So:
if dict_x.items() <= dict_y.items(): # Use .viewitems() instead of .items() on Python 2.7
will only return true if every key/value pair in dict_x also appears in dict_y.
This won't change anything in terms of big-O performance, but it does make the code somewhat cleaner:
for dict_x in dict_list1:
for dict_y in dict_list2:
if dict_x.items() <= dict_y.items():
print('YAY')
break
Note that creating the views costs something (it's just a fixed cost, not dependent on dict size), so if performance matters, it may be worth caching the views; doing so for dict_list1 is free:
for dict_x in dict_list1:
dict_x_view = dict_x.items()
for dict_y in dict_list2:
if dict_x_view <= dict_y.items():
print('YAY')
break
but some eager conversions would be needed to cache both:
# Convert all of dict_list2 to views up front; costs a little if
# not all views end up being tested (we always break before finishing)
# but usually saves some work at the cost of a tiny amount of memory
dict_list2_views = [x.items() for x in dict_list2]
for dict_x in dict_list1:
dict_x_view = dict_x.items()
for dict_y_view in dict_list2_views:
if dict_x_view <= dict_y_view:
print('YAY')
break
You could also collapse the loop using any (which removes the need to break since any short-circuits), so the first (simplest) check could become:
for dict_x in dict_list1:
if any(dict_x.items() <= dict_y.items() for dict_y in dict_list2):
print('YAY')
This could be further collapsed to a single list comprehension that results in the various matches, but at that point the code is going to be pretty cramped/ugly:
for _ in (dict_x in dict_list1 if any(dict_x.items() <= dict_y.items() for dict_y in dict_list2)):
print('YAY')
though without knowing what you'd really do (as opposed to just printing YAY) that's getting a little pointless.
