Python Numba - Convert DataFrame series object to numpy array - python-3.x

Question

I have a pandas dataframe with strings I am trying to use the set operation using python numba to get the unique characters in the column that contains strings in the dataframe. Since, numba does note recognize pandas dataframes, I need to convert the string column to an numpy array. However, once converted the column shows the dtype as a object. Is there a way that I could convert the pandas dataframe (column of strings) to a normal array (not an object array)
Please find the code for your understanding.
z = train.head(2).sentence.values #Train is a pandas DataFrame
z
Output:
array(["Explanation\nWhy the edits made under my username Hardcore Metallica Fan were reverted? They weren't vandalisms, just closure on some GAs after I voted at New York Dolls FAC. And please don't remove the template from the talk page since I'm retired now.89.205.38.27",
"D'aww! He matches this background colour I'm seemingly stuck with. Thanks. (talk) 21:51, January 11, 2016 (UTC)"],
dtype=object)
Python Numba code:
#njit
def set_(z):
x = set(z.sum())
return x
set_(z)
Output:
---------------------------------------------------------------------------
TypingError Traceback (most recent call last)
<ipython-input-51-9d5bc17d106b> in <module>()
----> 1 set_(z)
~/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/dispatcher.py in _compile_for_args(self, *args, **kws)
342 raise e
343 else:
--> 344 reraise(type(e), e, None)
345 except errors.UnsupportedError as e:
346 # Something unsupported is present in the user code, add help info
~/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/six.py in reraise(tp, value, tb)
656 value = tp()
657 if value.__traceback__ is not tb:
--> 658 raise value.with_traceback(tb)
659 raise value
660
TypingError: Failed at nopython (nopython frontend)
Internal error at <numba.typeinfer.ArgConstraint object at 0x7fbe66c01a58>:
--%<----------------------------------------------------------------------------
Traceback (most recent call last):
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/errors.py", line 491, in new_error_context
yield
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/typeinfer.py", line 194, in __call__
assert ty.is_precise()
AssertionError
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/typeinfer.py", line 138, in propagate
constraint(typeinfer)
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/typeinfer.py", line 195, in __call__
typeinfer.add_type(self.dst, ty, loc=self.loc)
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/contextlib.py", line 99, in __exit__
self.gen.throw(type, value, traceback)
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/errors.py", line 499, in new_error_context
six.reraise(type(newerr), newerr, tb)
File "/home/ec2-user/anaconda3/envs/tensorflow_p36/lib/python3.6/site-packages/numba/six.py", line 659, in reraise
raise value
numba.errors.InternalError:
[1] During: typing of argument at <ipython-input-50-566e4e12481d> (3)
--%<----------------------------------------------------------------------------
File "<ipython-input-50-566e4e12481d>", line 3:
def set_(z):
x = set(z.sum())
^
This error may have been caused by the following argument(s):
- argument 0: Unsupported array dtype: object
This is not usually a problem with Numba itself but instead often caused by
the use of unsupported features or an issue in resolving types.
To see Python/NumPy features supported by the latest release of Numba visit:
http://numba.pydata.org/numba-doc/dev/reference/pysupported.html
and
http://numba.pydata.org/numba-doc/dev/reference/numpysupported.html
For more information about typing errors and how to debug them visit:
http://numba.pydata.org/numba-doc/latest/user/troubleshoot.html#my-code-doesn-t-compile
If you think your code should work with Numba, please report the error message
and traceback, along with a minimal reproducer at:
https://github.com/numba/numba/issues/new
Would anyone be able to help me in this regard.
Thanks & Best Regards
Michael