Python 3. How to create triangels and patterns

So, i am trying to learn python 3 on my own and found this question on the web. i know how to use loops but not how to use nested loops. IF anyone can help it would be nice cuz all i managed to do was triange 1:

Write code that will display nested triangles as seen in the diagrams below. At each level the complete triangle for the previous level is placed into an extra outer triangle. The user should be asked to input the two characters to be used and the width of the innermost triangle, which must be odd. In addition to the test for negative input the function should test whether the supplied number is odd and display an appropriate message if it is not.