How to get name of streams in MinibatchSource?

Question

How can I get the names of each of the streams in a MinibatchSource?

Can I get the names associated with with the stream information returned by stream_infos?

minibatch_source.stream_infos()

I also have a follow-up-question:

The result from: print(reader_train.streams.keys()) is dict_keys(['labels', 'features'

How does these names relate to the construction of the MiniBatchSource, which is done like this?

return MinibatchSource(ImageDeserializer(map_file, StreamDefs(
    features = StreamDef(field='image', transforms=transforms), # first column in map file is referred to as 'image'
    labels   = StreamDef(field='label', shape=num_classes)      # and second as 'label'
)))

I would have thought that my streams would be named ‘image’ and ‘label’, but they were named ‘labels’ and ‘features’.

I guess those names are somehow default names?

Answer 1

For your original question:

minibatch_source.streams.keys()

See for example this tutorial under the section "A Brief Look at Data and Data Reading".

For your followup question: The names returned by keys() are the arguments of StreamDefs(). This is all you need in your program. If you define your MinibatchSource like this

return MinibatchSource(ImageDeserializer(map_file, StreamDefs(
image = StreamDef(field='image', transforms=transforms), # first column in map file is referred to as 'image'
label = StreamDef(field='label', shape=num_classes)      # and second as 'label')))

then the names will match. You can choose any names you want but the value of the field inside StreamDef() should match the source (which depends on your input data and the Deserializer you are using).