What does this error mean when I use `os.walk` to get the files path on python 3?

Question

the error is too long so I haven't put it in the title. Here is the error:

Traceback (most recent call last):
  File "./auto_change_shebang_and_permission.py", line 12, in <module>
    shebang = f.readline()
  File "/usr/lib/python3.4/codecs.py", line 319, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x8c in position 3: invalid start byte

However I've never seen this error before. I written a program to auto change the SheBang on Linux and it use os.walk to get the files path and open them, here is the program:

for root, dirs, files in os.walk(sys.argv[1]):                               
    for name in files:
        # to except the hidden file                                            
        if root[:3] == './.':                                                
            pass                                                             
        elif name[0] == '.':                                                 
            pass    
        # open the file, read the SheBang, and change it.
        else:                                                              
           with open(os.path.join(root, name), 'r') as f:                    
               shebang = f.readline()                                        
               if shebang[:2] != '#!':                                       
                   with open(os.path.join(root, name), 'w') as e:            
                       e.write('#!/usr/bin/env python3\n'+shebang+f.read())  
               else:                                                         
                   if shebang != '#!/usr/bin/env python3':                   
                       with open(os.path.join(root, name), 'w') as e:        
                           e.write('#!/usr/bin/env python3\n'+f.read())      

               os.chmod(os.path.join(root, name), 493)

It's working, but it will raise that error. I don't know where is wrong.

Answer 1

Okay, now I understand what's wrong. Because if root[:3] == './.' only works when the sys.argv[1] is . .

Then, like @AnandSKumar said. The program got a file that is not a text file.

So now I edited my code like this:

if fnmatch(root, sys.argv[1]+'/.*'):
    pass

And now it's working so good, thanks @AnandSKumar.