I try to write an iterator class:
class FileIterator(object):
def __init__(self,file_object):
self.fin = file_object
# other initialization code here ...
def __iter__(self):
return self
def next(self):
# special code that reads from the file and converts to
Pythonic data...
This iterator I want to use with regular binary file objects. My
requirement is to be able to create many iterators for the same file
object, and use them from many threads - which is not straightforward.
Of course I do not want to save file positions in the iterators, use
locking on the file, and call seek() every time I need to read from the
file. Instead of that, I try to re-open the file for each iteator. The
trivial way to do it is:
class FileIterator(object):
def __init__(self,file_object):
self.fin = open(file_object.name,"rb")
self.fin.seek(file_object.tell())
...
However, it won't work for temporary files. Temporary files are just
file-like objects, and their name is '<fdopen>'. I guess I could open a
temporary file with os.open, and then use os.dup, but that is low level
stuff. Then I have to use os.* methods, and the file object won't be
iterable. tempfile.NamedTempFile is not better, because it cannot be
reopened under Windows.
So the question is, how do I create my iterator so that:
* under Windows and Unix
* many iterators can be used for the same underlying file, from many
threads
* with a normal binary file
* and also with temporary files
A workaround would be to create a temporary directory, and then create
real files inside the temporary directory. If there is no better way to
do it, I'll do that.
Thanks
Laszlo
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