Python iterator Memory error

Question

I'm running this program to create a iterator but I get a memory error even before it started printing anything.

def test():
        for x in range(10000000000000):
                yield x

for x in test():
        print 'hi'

output:

tutorial@p1980:~/tej$ python itertest.py
Traceback (most recent call last):
  File "itertest.py", line 7, in <module>
    for x in test():
  File "itertest.py", line 4, in test
    for x in range(10000000000000):
MemoryError

And what is your question? range(10000000000000) creates a pretty big list. If I just run x = range(10000000000000), the process uses up to 56GB of memory before it dies. — Felix Kling
– Felix Kling, Commented May 15, 2015 at 2:16

Greg Hewgill · Accepted Answer · 2015-05-15 02:27:58Z

3

You appear to be using Python 2. In this case, use xrange() instead of range(). The xrange() function returns an object that works like an iterator instead of a list.

In Python 3, range() returns an object that works like an iterator, and does not offer an xrange() function.

edited May 15, 2015 at 2:27

answered May 15, 2015 at 2:15

Greg Hewgill

1.0m192 gold badges1.2k silver badges1.3k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Greg Hewgill Over a year ago

@Shashank: The difference is semantic. Python 2 actually returns an "xrange object", which for the above purpose is functionally identical to an iterator. Anyway, I've edited the answer.

TigerhawkT3 Over a year ago

In Python 3, range() creates a neat range object with some very useful optimizations. On top of that, Python 3 lets you print that generator with just print(*test(), sep='\n').

Shashank Over a year ago

Still, it would be better to say that it returns an iterable object. Even if you understand that it doesn't exactly return an iterator, it would be best to avoid confusing others with the term. Python even has a specific error for this: next(xrange(10)) (or range in Python 3.x) yields: TypeError: xrange object is not an iterator

Greg Hewgill Over a year ago

@Shashank: I've already updated the answer to avoid the misleading terminology. I feel that further explanations of the details of the internal implementation in Python would detract from the answer. Readers may refer to these comments if further detail is desired.

Collectives™ on Stack Overflow

Python iterator Memory error

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related