resized_image = Image.resize((100,200));
Image is Python-Pillow Image class, and i've used the resize function to resize the original image,
How do i find the new file-size (in bytes) of the resized_image without having to save to disk and then reading it again
You can't. PIL deals with image manipulations in memory. There's no way of knowing the size it will have on disk in a specific format.
You can save it to a temp file and read the size using os.stat('/tmp/tempfile.jpg').st_size
How to get image size in python-pillow after resize?