pickle docs say bytes in one place, strings in another

[Skaperen]

for pickle documentation i read "The pickle and marshal modules can turn many Python data types into a stream of bytes and then recreate the objects from the bytes." and '“Pickling” is the process whereby a Python object hierarchy is converted into a byte stream, and “unpickling” is the inverse operation, whereby a byte stream is converted back into an object hierarchy.' and i also read "file must have a write() method that accepts a single string argument."

which can i use, bytes and/or strings?

i want to send picked data to a subprocess over a pipe, but the pipe wants data only in bytes. do i need to encode it before sending it? is there a way to send it over the pipe, directly?