struct is saving 4 bytes instead of 2

[TonyB]

Using UBUNTU python 2.4.3 I'm using struct to save a variable to a
file.  My goal is to save it as a 2 byte signed integer.  Its being
saved using:

f.write(struct.pack('h',thevariable))

When I inspect the file with a hex editor it show that the variable is
being saved as 4 bytes.  How can I make it save the value as 2 bytes?

Tony