Pass a Julia string to Python as an iterable



Is it possible to pass a Julia String (or alternatively a Vector{UInt8} or IOBuffer wrapping the same) to Python as an iterable object?

I have attempted to pass the data directly, and also as part of a Julia generator (e.g. (c for c in s)) to no avail.

The use case is calling upload_object_via_stream in LibCloud.jl without writing a file to disk.


is there a pycall convert function you can overload?


Please provide an example of the issue. PyCall converts Julia strings to Python ‘str’, and ‘str’ is iterable, so the following works as expected:

pyeval("[x for x in y]", y="hello")

using LibCloud.Storage

storage = StorageDriver(region, aws_key, aws_secret)
bucket =  get_container(storage, bucketname)
upload_object_via_stream(container, "a test string", "cloudfile")

ERROR: PyError (:PyObject_Call) <type 'exceptions.AttributeError'>
AttributeError("'str' object has no attribute 'next'",)

I would like to be able to pass some data in memory (in this case “a test string”) in a way over which Python would be happy to iterate. I get the impression I may misunderstand what type of object Python is expecting…

Any suggestions?


Python strings don’t have a next attribute. Maybe it is expecting a bytearray, which you can pass from Julia via Vector{UInt8}("a test string").


As per the original post, this also doesn’t work, failing with the same error:

upload_object_via_stream(container, Vector{UInt8}("a test string"), "cloudfile")

ERROR: PyError (:PyObject_Call) <type 'exceptions.AttributeError'>
AttributeError("'bytearray' object has no attribute 'next'",)


Well, you need to read the documentation for the Python module. Figure out what works in Python, and then translate it to the corresponding Julia code.


According to the documentation the argument should be:

iterator (object) – An object which implements the iterator interface.

I will do some digging.

Thanks for your time.


Use StringIO.


This works perfectly, thank you.