I have the following code, which just print the key/value pairs in a dict (the pairs are sorted by keys):
for word, count in sorted(count_words(filename).items()): print word, count
iteritems() instead of
items() produces the same output
for word, count in sorted(count_words(filename).iteritems()): print word, count
Now, which one should I choose in this situation? I consulted the Python tutorial but it doesn’t really answer my question.
In Python 2.x both will give you the same result. The difference between them is that
items constructs a list containing the entire contents of the dictionary whereas
iteritems gives you an iterator that fetches the items one at a time. In general
iteritems is a better choice because it doesn’t require so much memory. But here you are sorting the result so it probably won’t make any significant difference in this situation. If you are in doubt
iteritems is a safe bet. If performance really matters then measure both and see which is faster.
In Python 3.x
iteritems has been removed and
items now does what
iteritems used to do, solving the problem of programmers wasting their time worrying about which is better. 🙂
As a side note: if you are counting occurrences of words you may want to consider using
collections.Counter instead of a plain dict (requires Python 2.7 or newer).
As per Marks answer: In Python 2, use
iteritems(), in Python 3 use
And additionally; If you need to support both (and don’t use
counts = count_words(filename) for word in sorted(counts): count = counts[word]