I don't like l as variable name (looks too much like number one), so I changed it a little:
for fn in os.listdir("C:/Bilder"):
print fn # test
if fnmatch.fnmatch(fn, 'IMG*'):
fn = fn.replace(fn, "HH")
"""my result -->
Hello, thank you for your answer. I did not expalin exactly what I wanted to do in this little code-snippet.
I actually want to rename all files in the directory "C:\\Bilder" with the name IMG to HH.
But the example you showed me did not do that.
Is it possible for you to show me how to do that?