Change the file extension for files in a folder in Python
Question: I would like to change the extension of the files in specific folder. i read
about this topic in the forum. using does ideas, I have written following code
and I expect that it would work but it does not. I would be thankful for any
guidance to find my mistake.

    
    
       import os,sys
       folder = 'E:/.../1936342-G/test'
       for filename in os.listdir(folder):
               infilename = os.path.join(folder,filename)
               if not os.path.isfile(infilename): continue
               oldbase = os.path.splitext(filename)
               infile= open(infilename, 'r')
               newname = infilename.replace('.grf', '.las')
               output = os.rename(infilename, newname)
               outfile = open(output,'w')
    


Answer: The `open` on the source file is unnecessary, since `os.rename` only needs the
source and destination paths to get the job done. Moreover, `os.rename` always
returns `None`, so it doesn't make sense to call `open` on its return value.

    
    
    import os,sys
    folder = 'E:/.../1936342-G/test'
    for filename in os.listdir(folder):
           infilename = os.path.join(folder,filename)
           if not os.path.isfile(infilename): continue
           oldbase = os.path.splitext(filename)
           newname = infilename.replace('.grf', '.las')
           output = os.rename(infilename, newname)
    

I simply removed the two `open`. Check if this works for you.

