python - What does "raw image data, as a byte string" mean? -

i doing program edit tags on mp3 using python, right using mutagen module , in order embed image cover art mp3 file using id3v4 standards have add apic frame using this.

but don't understand have put in parameters encoding,mime , data.

i looked example here , came this:

frame= apic(3,"image/jpg",3,"cover",open("albumcover.jpg")) 

but don't know first 3 means? why when put "utf-8" doesn't work? , open() function doesn't work, returns error this:

traceback (most recent call last):   file "<pyshell#104>", line 1, in <module>     frame= apic(3,"image/jpg",3,"cover",open("albumcover.jpg"))   file "c:\python34\lib\site-packages\mutagen\id3\_frames.py", line 65, in __init__     setattr(self, checker.name, checker.validate(self, val))   file "c:\python34\lib\site-packages\mutagen\id3\_specs.py", line 184, in validate     raise typeerror("%s has bytes" % self.name) typeerror: data has bytes 

and when put "b"

frame= apic(3,"image/jpg",3,"cover",open("albumcover.jpg","b")) 

it returns

traceback (most recent call last):   file "<pyshell#106>", line 1, in <module>     frame= apic("utf-8","image/jpg",3,"cover",open("albumcover.jpg","b")) valueerror: must have 1 of create/read/write/append mode , @ 1 plus 

so should put there?

and tried open("albumcover.jpg").read() , doesn't work.

you need open file in either of - read (rb) or write (wb) or append (ab)modes (b - indicating binary file , read bytes instead of strings) .

for case, think read mode sufficient, try -

frame= apic(3,"image/jpg",3,"cover",open("albumcover.jpg","rb").read()) 

the rb indicates need open file in read mode , binary file, calling .read() function on causes read bytes file , return it.