How do I get number of files in a particular directory.

[blur959]

Hi, I tried that, but it doesn't seem to work. My file directory has
many different files extensions, and I want it to return me a number
based on the number of files with similar files extensions. But when I
tried running it, I get many weird numbers. Below is my code i had so
far and the result.

import os

directory = raw_input("Please input file directory. \n\n")
s = raw_input("Please input a name to replace. \n\n")
ext = raw_input("input file ext")

for files in os.listdir(directory):
    if ext in files:
        file_number = len(files)
        print file_number


The result is:
13
13
13
6
15
8
10
10
8
7
5

where the result should be just 11. Can anyone help me? Thanks.