def isalpha(obj):
    """
    Test if the argument is a string representing a number.

    :param obj: Object
    :type  obj: any

    :rtype: boolean

    For example:

        >>> import pmisc
        >>> pmisc.isalpha('1.5')
        True
        >>> pmisc.isalpha('1E-20')
        True
        >>> pmisc.isalpha('1EA-20')
        False
    """
    try:
        float(obj)
        return isinstance(obj, str)
    except:
        return False
