do you mean strings ? If so, that's the normal way of using 'data' in python AFAIK (i.e. if you read from a file you'll get a string).

Strings in Python don't support mutable slices. Reading from the buffer is easy and intuitive, but writing data on a buffer is not documented.
buf = gst.Buffer (size); buf[:size] = data

proper usage :
  buf.data = "this is the content of my buffer"
or even simpler:
  buf = gst.Buffer ("this is the content of my buffer")

The example you gave is completely bogus, you can't create a gst.Buffer() with an integer argument. That should have errored out.

There's no gst-python specific documentation. Closing bug.

I'm sorry for the wrong constructor.

>>> buf = gst.Buffer ()
>>> buf.data = "test"
Traceback (most recent call last):

+ Trace 214184

This is what I'm using now:
>>> buf = gst.buffer_new_and_alloc (4)
>>> buf[:4] = "test"
>>> print buf
test
>>> 

So please document:
1. gst.Buffer (str) constructor, which is not in the C core reference so I couldn't realize that and the only constructor in the pygst reference has clearly no arguments
2. assignable/deletable slices

Closing this bug now, gst-python is only an extension module to pygi now and this bug doesn't make much sense anymore in this context.