look at file type and determine if the type is correct, print statement, python

[jackie123]

working on a program that takes a file and determines what type it is. It must be a .wav or .jpg file to be correct, and if it is not one of those, it will display a message that says to choose a correct file type. However, I am stuck on how to get it to determine what type of file is being chosen, since for this program I am not allowed to use f.endswith()
I have tried something like this but it is giving me a syntax error for the line "if f[f.rfind:] == '.wav':" i am not sure what the error is here, could you help me with what the issue may be?

def fileType(): 
f = pickAFile 
print f
print "File Type:", f[f.rfind('.'):] 
  if f[f.rfind('.'):] == '.wav': 
    print "A sound file was selected." 
  if f[f.rfind('.'):] == '.jpg' : 
    print "An image file was selected 
  else: 
    print " This was an incorrect file type." 
    print " Please chose a .wav or .jpg file."

[dwblas]

Assuming that you identify a file by the name ending, I always use endswith() or if fname[-4:]==. Note that the variable, pickAFile, may not be known to the function unless it is a global variable.

[jackie123]

yes i know that endswith() would work best but it is not allowed in this program. How would I go about fixing what I have above?