[Python-ideas] `to_file()` method for strings

[Chris Barker - NOAA Federal]

Just to make sure I follow: Chris, you're proposing a modification to
garbage collection to clean up `open()` if `open()` is used by not closed
and not assigned to anything so that `open(file).write(stuff)` is safe?


Well, I wouldn't call it a proposal, more a random inspiration that popped
up when thinking about this thread.

That sounds brilliant to me, and totally meets my goal of having a
"one-step" method for writing to disk that doesn't require users to develop
a two-step mental model. If it's feasible (I have nothing but the most
basic understanding of how the garbage collector works), that would totally
obviate my desire to have a `to_file()` method on strings.


IIUC, in the current cPython implementation, you do indeed have that --
I've used it for years, long before context managers existed, and still do
for quickie scripts.

CPython uses a reference counting scheme: each time an object is
referenced, its count is increased, each lost reference, and it is
decreased. When the count goes to zero, the object is deleted. So in:

Data = open(file name).read()

The file object is created, given a refount of one. Then the read() method
is called, creating a string, then bound to the name Data. When the next
line is reached, the recount of the file object is reduced to zero, and the
object is deleted. And the internal file pointer is closed before deleting
the object.

The "trick" is that the Python language spec does not require this kind of
garbage collection. So jython, or pypy, or ironPython may not clean up that
file object right away, it could hang around in an open and unflushed state
until the garbage collector gets around to cleaning it up.

But for short scripts, it'll get cleaned up at the end of the script
anyway.

The thing is that while I, at least, think it's a fine practice for
scripting, it's really not a good idea for larger system development.

Thus the general advise to use "with".

As for any proposal, it dawned on me that while we don't want Python to
require any particular garbage collecting scheme, I wonder if it would be
possible (or desirable) to specify that temporary objects used on one line
of code, and never referenced any other way, get deleted right away.

It's actually very common to create a lot of temporaries on a line of code
-- when you chain operations or methods. So it might be a small performance
tweak worth doing (or it may not :-) )

-CHB
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