在python中不可迭代的列表或元组

Question

i am looking for a data collection which is NOT iterable.

reason behind it is, there is some code which merges multiple results by adding them to a new list and then calling the "list.extend" function.

i tried tuple, but it is iterable, im looking for a built in collection which is not iterable.

what it does:

>>> t1 = tuple([1,2,3])
... t2 = tuple([4,5,6])
... l = list()
... 
>>> l.extend(t1)
>>> l.extend(t2)
>>> 
>>> l
[1, 2, 3, 4, 5, 6]

what i want l to be is:

[(1,2,3), (4,5,6)]

please bare in mind i can only change the t1, t2 variables.... it has to go through extent.

Answer 1

Your problem is not that the tuple is iterable. Making the tuple non-iterable won't help because extending a list with a non-iterable simply doesn't work.

>>> l = []
>>> l.extend(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
>>> 

What you need to do, is wrap your tuples in a list:

>>> t1 = (1,2,3)
>>> t2 = (4,5,6)
>>> l.extend([t1])
>>> l.extend([t2])
>>> l
[(1, 2, 3), (4, 5, 6)]
>>> 

You can also extend the list with both tuples at the same time:

>>> l.extend([t1,t2])
>>> l
[(1, 2, 3), (4, 5, 6), (1, 2, 3), (4, 5, 6)]
>>> 

Answer 2

You can use append feature of a list eg:-

>>> t1 = tuple([1,2,3])
>>> t2 = tuple([4,5,6])
>>> l = list()
>>> l.append(t1)
>>> l.append(t2)
>>> l # [(1,2,3), (4,5,6)]

Answer 3

you could create a child class of list with extend and __iadd__ methods overridden, so if a tuple is passed as a parameter, it appends instead of extending:

class MyList(list):
    def __fake_extend(self,other):
        if isinstance(other,tuple):
            self.append(other)
        else:
            list.extend(self,other)

    def __iadd__(self,other):
        self.__fake_extend(other)
        return self
    def extend(self,other):
        self.__fake_extend(other)

t1 = (1,2,3)
t2 = (4,5,6)

l = MyList()

l.extend(t1)
l.extend(t2)
l.extend([4,2,4,5])
print(l)

result:

[(1, 2, 3), (4, 5, 6), 4, 2, 4, 5]

the tuples have been appended, the items of the list as well (since they were contained in a list not a tuple )