Question

def __init__(self, maximum, start=0, step=1):
        """Sets the maximum, start, and step"""
        try:
            self.maximum = math.ceil(maximum)
            self.start = math.ceil(start)
            self.step = math.ceil(step)
        except TypeError:
            return "Error, attributes must be of type int or float"
    def __iter__(self):
        """Iterates over the range"""
        return iter(range(self.start, self.maximum, self.step))

is the relevant code. Whenever I call, say:

j = crange.ChangeableRange(4)
list(j)

I get the error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "crange.py", line 16, in __iter__
    return iter(range(self.start, self.maximum, self.step))
TypeError: 'str' object cannot be interpreted as an integer

Why? How do I fix this?

Answer 1

The range function expects integers for arguments. It looks like you’ve created a string for either start, maximum, or step with something like self.maximum = int(math.ceil(maximum)).

Also note that in Python 2, the math.ceil function returns a float value, so those would need to be converted to integers.

In Python 3, your code works fine:

>>> import math
>>> class ChangeableRange:
        def __init__(self, maximum, start=0, step=1):
            """Sets the maximum, start, and step"""
            try:
                self.maximum = math.ceil(maximum)
                self.start = math.ceil(start)
                self.step = math.ceil(step)
            except TypeError:
                return "Error, attributes must be of type int or float"
        def __iter__(self):
            """Iterates over the range"""
            return iter(range(self.start, self.maximum, self.step))


>>> j = ChangeableRange(4)
>>> print(list(j)) 
[0, 1, 2, 3]