Answers:
这是一个布尔值:
if (not suffix == "flac" ) or (not suffix == "cue" ): # WRONG! FAILS
print filename + ' is not a flac or cue file'
但
if not (suffix == "flac" or suffix == "cue" ): # CORRECT!
print filename + ' is not a flac or cue file'
(not a) or (not b) == not ( a and b )
,仅当a和b均为true时为false
not (a or b)
仅当a和be均为假时才为true。