This little bag is called a “Japanese knot bag“. This Japanese-style bag closes by sliding the long handle in the short one and is worn at the wrist.
It belongs in the “click” bags family : Cell phone, Lipstick, ID, Cash, Keys. This is a small bag made to carry the bare necessities.
This bag is lined and reversible if desired.
There are several variations for the “Japanese knot bag”, this particular model comes from the Vogue pattern 7354.
You can find free patterns on the web : here (pdf) or here (english too). And finally Martha Stewart version right here.
The Vogue pattern contains different 7 types of evening bags. The knot bag is view A.
If I recall correctly, I think that my first time sewing it, I did not found the drawings very clear when it came to sewing the lining to the bag, but by basting fist it’s easy to see if you are on the right path.
Caution! Sewing this bag quickly becomes addictive!