Python range() and zip() object type

Question

I understand how functions like range() and zip() can be used in a for loop. However I expected range() to output a list - much like seq in the unix shell. If I run the following code:

a=range(10)
print(a)

The output is range(10), suggesting it's not a list but a different type of object. zip() has a similar behaviour when printed, outputting something like

<zip object at "hexadecimal number">

So my question is what are they, what advantages are there to making them this, and how can I get their output to lists without looping over them?

Answer 1

You must be using Python 3.

In Python 2, the objects zip and range did behave as you were suggesting, returning lists. They were changed to generator-like objects which produce the elements on demand rather than expand an entire list into memory. One advantage was greater efficiency in their typical use-cases (e.g. iterating over them).

The "lazy" versions also exist in Python 2.x, but they have different names i.e. xrange and itertools.izip.

To retrieve all the output at once into a familiar list object, you may simply call list to iterate and consume the contents:

>>> list(range(3))
[0, 1, 2]
>>> list(zip(range(3), 'abc'))
[(0, 'a'), (1, 'b'), (2, 'c')]