StreamFinalizer

ClassPrivateContextSource

with StreamFinalizer(
    fobj: IO[Any]@StreamFinalizer,
    truncate: bool = False,
    close: bool = False,
    callback_on_exit: Callable[[_IO], None] | None = None
) as _fobj:
    _fobj: IO[Any]@StreamFinalizer

Finalizer for a stream IO when the stream has been delivered.

This class will be used by ServiceData for safely maintain the file object while serving the file stream.

Arguments

Argument	Type	Required	Description
fobj	IO[Any]		The file-like object to be managed when exiting the finalizer environment.
truncate	bool		A flag. If set, will trucate the file when exiting the context. This flag should not be used when the IO is read-only.
close	bool		A flag. If set, will close the file handle when exiting the context.
callback_on_exit	Callable[[_IO], None] | None		The callback function that will be called when exiting from the context. This method will be called before the file is truncated or closed.

Examples

Automatically close the file when exiting from the context

Codes

import os
from dash_file_cache.utilities import StreamFinalizer, TempDir


temp_dir = TempDir()
fobj = open(os.path.join(temp_dir.path, "test.txt"), "w")
with StreamFinalizer(fobj, close=True) as _fobj:
    _fobj.write("test")

print(fobj.closed)

Results

True

Automatically cut the file to an empty file when exiting from the context

Codes

import os
from dash_file_cache.utilities import StreamFinalizer, TempDir


temp_dir = TempDir()
fobj = open(os.path.join(temp_dir.path, "test.txt"), "w")
with StreamFinalizer(fobj, truncate=True) as _fobj:
    _fobj.write("test")

print(fobj.closed)
if not fobj.closed:
    fobj.seek(0, os.SEEK_END)
    print(fobj.tell())
    fobj.close()

Results

False
0