python - Why isn't isnumeric working?

Question

I was going through a very simple python3 guide to using string operations and then I ran into this weird error:

In [4]: # create string
        string = 'Let's test this.'

        # test to see if it is numeric
        string_isnumeric = string.isnumeric()

Out [4]: AttributeError                            Traceback (most recent call last)
         <ipython-input-4-859c9cefa0f0> in <module>()
                    3 
                    4 # test to see if it is numeric
              ----> 5 string_isnumeric = string.isnumeric()

         AttributeError: 'str' object has no attribute 'isnumeric'

The problem is that, as far as I can tell, str DOES have an attribute, isnumeric.

Answer 1

No, str objects do not have an isnumeric method. isnumeric is only available for unicode objects. In other words:

>>> d = unicode('some string', 'utf-8')
>>> d.isnumeric()
False
>>> d = unicode('42', 'utf-8')
>>> d.isnumeric()
True