python - TypeError: 'zip' object is not subscriptable

Question

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 me the following error:

return " ".join(list[zip(*ngram)[0]])
TypeError: 'zip' object is not subscriptable

Can someone help?

Answer 1

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))