UnBoundLocalError

[Seaninho]

Hello to everyone!

I'm trying to create a code using Python but I have a problem.
It gives me this error:

Error:
File "/opt/miniconda3/bin/sfipick", line 268, in <module>
    image = rsf2image(0)
  File "/opt/miniconda3/bin/sfipick", line 67, in rsf2image
    return img
UnboundLocalError: local variable 'img' referenced before assignment

I will post here the part of the code where the problem is:

def rsf2image(i3):
    global byte
    ppm = '%s%d.ppm' % (name,i3)
    if not os.path.isfile(ppm):
        command = '< %s %s n3=1 f3=%d | %s %s | %s %s > %s' % \
            (byte,sfwindow,i3,sfgrey,args,ppmpen,args,ppm)
        if os.system(command) or not os.path.isfile(ppm):
            sys.stderr.write('Failed to execute "%s"\n\n' % command)
            sys.exit(3)
        ppms.append(ppm)
    img = PhotoImage(file=ppm)
    return img

...
image = rsf2image(0)

Can someone please help me with this?

Thank you very much