问题
Let's say that I have a Python dictionary, but the values are a tuple:
E.g.
dict = {"Key1": (ValX1, ValY1, ValZ1), "Key2": (ValX2, ValY2, ValZ2),...,"Key99": (ValX99, ValY99, ValY99)}
and I want to retrieve only the third value from the tuple, eg. ValZ1, ValZ2, or ValZ99 from the example above.
I could do so using .iteritems(), for instance as:
for key, val in dict.iteritems():
ValZ = val[2]
however, is there a more direct approach?
Ideally, I'd like to query the dictionary by key and return only the third value in the tuple...
e.g.
dict[Key1] = ValZ1 instead of what I currently get, which is dict[Key1] = (ValX1, ValY1, ValZ1) which is not callable...
Any advice?
回答1:
Just keep indexing:
>>> D = {"Key1": (1,2,3), "Key2": (4,5,6)}
>>> D["Key2"][2]
6
回答2:
Use tuple unpacking:
for key, (valX, valY, valZ) in dict.iteritems():
...
Often people use
for key, (_, _, valZ) in dict.iteritems():
...
if they are only interested in one item of the tuple. But this may cause problem if you use the gettext module for multi language applications, as this model sets a global function called _.
As tuples are immutable, you are not able to set only one item like
d[key][0] = x
You have to unpack first:
x, y, z = d[key]
d[key] = x, newy, z
回答3:
Using a generator expression!
for val in (x[2] for x in dict):
print val
You don't need to use iteritems because you're only looking at the values.
来源：https://stackoverflow.com/questions/7504081/query-python-dictionary-to-get-value-from-tuple