### 3.3 R exceptions

RPy implements a new exception type, called `RException`, which is derived from the base class of all exceptions `Exception`. This exception is raised when an error in the R interpreter occurred. The error message included in the exception is the message given by the R interpreter. For example:

    >>> RException
    <class rpy.RException at 0x8a72b44>
    >>>
    >>> r.t_test(1)
    Traceback (most recent call last):
      File "<stdin>", line 1, in ?
    rpy.RException: Error in t.test.default(1) : not enough x observations

Note that not all operations with `Robj` objects raise this exception. When using the sequence protocol on `Robj` objects, the exceptions raised are `IndexError`, in order to properly use the `for` loop (see Sequence protocol). Other functions, such as mode functions, raise `ValueError` (see Modes).