How to load index shards by gensim.similarities.Similarity？
shoresh's answer is correct. The key part that OP was missing was 
    index.save(output_fname)
While just creating the object appears to save it, it's really only saving the shards, which require saving a sort of directory file (via index.save(output_fname) to be made accessible as a whole object.
I'm working on something using gensim.
In gensim, var index usually means an object of gensim.similarities.<cls>.
At first, I use gensim.similarities.Similarity(filepath, ...) to save index as a file, and then loads it by gensim.similarities.Similarity.load(filepath + '.0'). Because gensim.similarities.Similarity default save index to shards file like index.0.
When index file becoming larger, it automatically seperate into more shards, like index.0,index.1,index.2......
How can I load these shards file? gensim.similarities.Similarity.load() can only load one file.
BTW: I have try to find the answer in gensim's doc, but failed.