Python : How to properly implement a raise an exception in a function

Question

I am trying to make a function that receives a list/array and returns the index of the maximum value in that sequence. The function should raise an exception if non-numerical values are present in the list.

def maxvalue(values):
    """
    Function that receives a list/array and returns the index of the maximum
    value in that sequence

    """    
    indices = []
    max_value = max(values)
    for i in range(len(values)):
        if type(i) not in (float, int): # raise an exception if the value is not float or integer
            raise TypeError("Only numberical values are allowed")
        if values[i] == max_value:
            indices.append(i)
    return indices

maxvalue([1, 1, 1.5, "e", 235.8, 9, 220, 220])

The function works when it receives a list containing floats and integers and doesn't work if there is a string in it.

How do I get the function to produce "TypeError("Only numberical values are allowed")" error quote when there is a str present in the list?

Currently, it produces "TypeError: '>' not supported between instances of 'str' and 'float'"

Answer 1

The 'Comparison' happens in max function which raises an exception.

You should do all checks, before your logic.

def maxvalue(values):
    """
    Function that receives a list/array and returns the index of the maximum
    value in that sequence

    """

    try:
        max_value = max(values)
    except TypeError:
        raise TypeError("Only numerical values are allowed")

    indices = []
    for idx, val in enumerate(values):
        if val == max_value:
            indices.append(idx)

    return indices

As you can see I am catching TypeError and re-raise it with different message. Also use enumerate in for loops.