Python 2.5 forced an API change in the APEv2 reading code. Some things which were case-insensitive are now case-sensitive. For example, given:
tag = APEv2() tag["Foo"] = "Bar" print "foo" in tag.keys()
Mutagen 1.7.1 and earlier would print “True”, as the keys were a str subclass that compared case-insensitively. However, Mutagen 1.8 and above print “False”, as the keys are normal strings.
print "foo" in tag
Still prints “True”, however, as __getitem__, __delitem__, and __setitem__ (and so any operations on the dict itself) remain case-insensitive.
As of 1.10.1, Mutagen no longer allows non-ASCII keys in APEv2 tags. This is in accordance with the APEv2 standard. A KeyError is raised if you try.
Compatibility / Bugs
Prior to 1.10.1, Mutagen wrote an incorrect flag for APEv2 tags that claimed they did not have footers. This has been fixed, however it means that all APEv2 tags written before 1.10.1 are corrupt.