Get with errors

Lesson 20 of 29 in Coddy's Calculator project using Python course.

As always let's take care of the errors can happen,

Empty string as input
Start index is over the length of the string

On both cases raise "End of string" message exception.

Challenge

Easy

Add error handling as described above to get_next.

Try it yourself

def calc(op, n1, n2=None):
    if not isinstance(n1, int) and not isinstance(n1, float):
        raise Exception('Invalid number "' + str(n1) + '"')

    if n2 is None:
        if op == '+' or op == 'add':
            return n1
        if op == '-' or op == 'sub':
            return -n1

        raise Exception('Invalid operator "' + op + '"')

    if not isinstance(n2, int) and not isinstance(n2, float):
        raise Exception('Invalid number "' + str(n2) + '"')

    if op == '+' or op == 'add':
        return n1 + n2
    if op == '-' or op == 'sub':
        return n1 - n2
    if op == '*' or op == 'mul':
        return n1 * n2
    if op == '/' or op == 'div':
        if n2 == 0:
            raise Exception("Division by zero")
        return n1 / n2
    if op == '%' or op == 'mod':
        if n2 == 0:
            raise Exception("Division by zero")
        return n1 % n2
    if op == '^' or op == 'pow':
        return n1 ** n2

    raise Exception('Invalid operator "' + op + '"')


def eval(lst):
    if not isinstance(lst, list):
        raise Exception('Failed to evaluate "' + str(lst) + '"')
    if len(lst) == 2:
        op = lst[0]
        n = lst[1]
        if not isinstance(n, list):
            return calc(op, n)

        if isinstance(n, list):
            n = eval(n)

        return calc(op, n)
    elif len(lst) == 3:
        op = lst[0]
        n1 = lst[1]
        n2 = lst[2]
        if not isinstance(n1, list) and not isinstance(n2, list):
            return calc(op, n1, n2)
        
        if isinstance(n1, list):
            n1 = eval(n1)
        if isinstance(n2, list):
            n2 = eval(n2)

        return calc(op, n1, n2)
    else:
        raise Exception('Failed to evaluate "' + str(lst) + '"')


LEVEL_TWO_OPERATORS = ['+', '-', 'add', 'sub']
LEVEL_ONE_OPERATORS = ['*', '/', '%', 'mul', 'div', 'mod']
FUNCTIONS_OPERATORS = ['^', 'pow']
def struct(lst):
    if not isinstance(lst, list) or len(lst) <= 1:
        raise Exception('Failed to structure "' + str(lst) + '"')

    if len(lst) == 2:
        return lst

    lst_cpy = lst
    operators_groups = [FUNCTIONS_OPERATORS, LEVEL_ONE_OPERATORS, LEVEL_TWO_OPERATORS]
    for operators_group in operators_groups:
        i = 0
        while i < len(lst):
            if lst[i] in operators_group:
                if len(lst) - 1 == i:
                    raise Exception('Failed to structure "' + str(lst_cpy) + '"')
                if len(lst) == 3:
                    return [lst[i], lst[i - 1], lst[i + 1]]
                temp = lst[:i - 1]
                temp.append([lst[i], lst[i - 1], lst[i + 1]])
                temp += lst[i + 2:]
                lst = temp
            else:
                i += 1

    return lst


NUMBERS = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9']
def get_next(s, i):
    res = ''
    if s[i] in NUMBERS or s[i] == '.':
        is_float = False
        while i < len(s) and (s[i] in NUMBERS or s[i] == '.'):
            res += s[i]
            if s[i] == '.':
                is_float = True
            i += 1

        if is_float:
            return float(res)
        return int(res)
    else:
        while i < len(s) and not (s[i] in NUMBERS or s[i] == '.'):
            res += s[i]
            i += 1

        return res