This isnt exactly what you asked for but it will get you started.
import os #bring in the necessary library to access your specific os
filename = raw_input("Enter file: ") #get user input
dirList = os.listdir('.') #get the current directory listing
if filename in dirList: #if the filename sought was in that dirlist....
print "file found: " + filename #display it
else: #otherwise...
print "That file does not exist."
solved How can I find a file in a directory [closed]