What is the Difference Between Python's `items()` and `iteritems()`?

Identifying Differences Between Python's Dictionary Methods: items() and iteritems()

While dict.items() and dict.iteritems() may appear to be interchangeable in Python 2, there are underlying nuances between the two. To understand these differences, let's delve into their respective roles.

As noted in the Python documentation, dict.items() provides a copy of the dictionary's key-value pairs as a list of tuples. This copy ensures that any changes made to the returned list will not affect the original dictionary.

On the other hand, dict.iteritems() returns an iterator over the key-value pairs. An iterator does not create a separate copy of the data but instead provides access to each item one at a time. This can be memory efficient when dealing with large dictionaries.

Despite their conceptual differences, it's important to note that in Python 2, both dict.items() and dict.iteritems() return references to the same underlying object. This object is a list of key-value pairs where each pair is a tuple.

However, this behavior has changed in Python 3. In Python 3, dict.items() now returns a view, which provides a live reference to the original dictionary. Therefore, changes made to the view will be reflected in the dictionary itself. The iteritems() method was removed in Python 3 as its functionality is now part of the modified dict.items().

In summary, dict.items() provides a copy of the dictionary's key-value pairs as a list in Python 2 and a view in Python 3. In contrast, dict.iteritems(), present only in Python 2, returns an iterator over the key-value pairs. Understanding these nuances is crucial for proper data handling and memory management in Python code.

The above is the detailed content of What is the Difference Between Python's `items()` and `iteritems()`?. For more information, please follow other related articles on the PHP Chinese website!