[FIXED] In Python 3, why do I get "TypeError: 'zip' object is not subscriptable" (or see a strange result instead of a list)?

Issue

I have a tagged file in the format token/tag and I try a function that returns a tuple with words from a (word,tag) list.

def text_from_tagged_ngram(ngram): 
    if type(ngram) == tuple:
        return ngram[0]
    return " ".join(zip(*ngram)[0]) # zip(*ngram)[0] returns a tuple with words from a (word,tag) list

In python 2.7 it worked well, but in python 3.4 it gives an error on the last line which says TypeError: 'zip' object is not subscriptable. Why did it stop working? How can I fix this?

---

_{Several other things changed from Python 2 to Python 3 in a parallel manner; see How to use filter, map, and reduce in Python 3.}

Solution

In Python 2, zip returned a list. In Python 3, zip returns an iterable object. But you can make it into a list just by calling list, as in:

list(zip(...))

In this case, that would be:

list(zip(*ngram))

With a list, you can use indexing:

items = list(zip(*ngram))
...
items[0]

etc.

But if you only need the first element, then you don't strictly need a list. You could just use next.

In this case, that would be:

next(zip(*ngram))

Answered By - khelwood