Use itertools.chain: from itertools import chain y_iter = chain(l1, l2) It yields all the items from l1 and then all the items from l2. Effectively concatenating the sequence of yielded items. In the process it consumes both.
Close is always necessary when dealing with files, it is not a good idea to leave open file handles all over the place. They will eventually be closed when the file object is garbage collected but you do not know when that will be and in the mean time you will be wasting system resources … Read more
According to Bjarne Stroustrup in Section 17.3.4.2 (p. 497) of The C++ Programming Language, 4th Edition: Unfortunately, initializer_list doesn’t provide subscripting. No further reason is given. My guess is that it’s one of these reasons: it’s an omission, or because the initializer_list class is implemented with an array and you’d have to do bounds checking … Read more
Iterable is a generic interface. A problem you might be having (you haven’t actually said what problem you’re having, if any) is that if you use a generic interface/class without specifying the type argument(s) you can erase the types of unrelated generic types within the class. An example of this is in Non-generic reference to … Read more
In Python 2.6 or better, the designed-in idiom for such behavioral checks is a “membership check” with the abstract base class in the collections module of the standard library: >>> import collections >>> isinstance(‘ciao’, collections.Iterable) True >>> isinstance(23, collections.Iterable) False >>> isinstance(xrange(23), collections.Iterable) True Indeed, this kind of checks is the prime design reason for … Read more
You can call listIterator method again to get an instance of iterator pointing at beginning of list: iter = list.listIterator();
I think you may be using the Arrays utility to get the List that you pass into that method. The object is indeed of type ArrayList, but it’s java.util.Arrays.ArrayList, not java.util.ArrayList. The java.util.Arrays.ArrayList version is immutable and its remove() method is not overridden. As such, it defers to the AbstractList implementation of remove(), which throws … Read more
Guava (formerly Google Collections) has Iterators.concat.
Iterators do not work recursively like that. You have to re-yield each result, by replacing explore(path) with something like for value in explore(path): yield value Python 3.3 added the syntax yield from X, as proposed in PEP 380, to serve this purpose. With it you can do this instead: yield from explore(path) If you’re using … Read more
Note the first part of the sentence you call out: For a QuerySet which returns a large number of objects that you only need to access once So the converse of this is: if you need to re-use a set of results, and they are not so numerous as to cause a memory problem then … Read more