If I have these two lists:
la = [1, 2, 3]
lb = [4, 5, 6]
I can iterate over them as follows:
for i in range(min(len(la), len(lb))):
print la[i], lb[i]
Or more pythonically
for a, b in zip(la, lb):
print a, b
What if I have two dictionaries?
da = {'a': 1, 'b': 2, 'c': 3}
db = {'a': 4, 'b': 5, 'c': 6}
Again, I can iterate manually:
for key in set(da.keys()) & set(db.keys()):
print key, da[key], db[key]
Is there some builtin method that allows me to iterate as follows?
for key, value_a, value_b in common_entries(da, db):
print key, value_a, value_b
There is no built-in function or method that can do this. However, you could easily define your own.
def common_entries(*dcts):
if not dcts:
return
for i in set(dcts[0]).intersection(*dcts[1:]):
yield (i,) + tuple(d[i] for d in dcts)
This builds on the "manual method" you provide, but, like zip, can be used for any number of dictionaries.
>>> da = {'a': 1, 'b': 2, 'c': 3}
>>> db = {'a': 4, 'b': 5, 'c': 6}
>>> list(common_entries(da, db))
[('c', 3, 6), ('b', 2, 5), ('a', 1, 4)]
When only one dictionary is provided as an argument, it essentially returns dct.items().
>>> list(common_entries(da))
[('c', 3), ('b', 2), ('a', 1)]
With no dictionaries, it returns an empty generator (just like zip())
>>> list(common_entries())
[]