Python 2: why xrange isn't called irange?

Question

This question is kind of philosophical. There is splendid itertools module in Python 2, providing, in particular, generator equivalents for Python built-in functions like map , filter , zip , or slice . And the equivalents are called imap , ifilter , izip , and islice , respectively. As I understand, the prefix i in their names means i ​terator. But there's the same thing about xrange : it is an equivalent of range returning generator object instead of large list. So, why isn't it called irange ? What does prefix x actually mean?

Answer 1

Because xrange() was added to the language before it had iterators and it is itself not an iterator.

• Iterators were added in PEP 234 , a proposal created in 2001.
• xrange() was added to Python in 1993 .

Python 1.0 was released in 1994, so xrange() was added very early on. The x most likely doesn't have a specific meaning here.

But xrange() is not really an iterator, it is an iterable ; you can iterate over it multiple times, unlike iterators. It is also a sequence, as it has a length and can be indexed.

As such the object has been renamed to range() (replacing the Python 2 range() function altogether), and its sequence behaviour has been further expanded.