Why is fileinput.input object not lost when going out-of-scope?

Question

In the following code I would expect than python is freeing fileinput.input when I'm returning in the middle my loop as it is going out-of-scope. However, when calling again my function fileinput tells me

raise RuntimeError, "input() already active"

Here is my code:

def func(inplace):
    for line in fileinput.input(sys.argv[1], inplace=inplace):
        [..]
        if condition:
             return True
        [..]

if func(False):
    func(True)

I would expect this behavior when using yield but not when using return.

I'm using Python 2.7.3.

Is there any way to force a reset of fileinput?

EDIT:

When calling fileinput.close() before returning it works. Why is it not done implicitly?

EDIT 2: Thanks to @MatsLindh

Replacing

for line in fileinput.input(sys.argv[1], inplace=inplace):

with

for line in fileinput.FileInput(sys.argv[1], inplace=inplace):

does what I want, because it returns an object which goes out-of-scope in a defined manner. I assumed that fileinput.input() does that, but no. It is using a global instance.

Answer 1

So you need to wrap fileinput.input() in a closing "context manager" which will **ensure*8 that .close() is called when you exit the block by using with ...::

from contextlib import closing

def func(inplace):
    with closing(fileinput.input(sys.argv[1], inplace=inplace)) as finput:
        for line in finput: 
            [..]
            if condition:
                return True
            [..]

Using a context manager on objects that implement the protocol; usually file objects and the like you ensure that cleaned operations are performed on exit of the with block.

---

Garbage collection can occur any time; and there are conditions around when objects are freed adn cleaned up. If you want the file object to be closed when you exit the block use with.