Write a program with a loop to compute the sum of all odd digits of an input python

Hi I'm currently in school for Computer science and I'm having problems with two of my codes, the first one pertains to the title. I have to create a program that takes only the odd digits of an input and sums them. I honestly have no idea how to approach this, this is all I have

Scanner in = new Scanner[System.in];

    int a;
    int b;

    System.out.println["Enter a number: "];
    a = in.nextInt[];

    while [a > 0] { 
        if [a.charAt[0] % 2 != 0] {

        }
    }

the second problem I have trouble with is write program with loops that computes the sum of all square between 1 and 100 [inclusive] This is the code i have

    int i=1;
    int j=0;

    while [i