Python : Find Second largest number in a given list

Python program to find the second largest number from a given list
Conditions : Without using remove(), set(), max(), sort() i.e without using built-in library functions
and without using the sorting algorithms

[shankarhogalennavar]

Thank you for sharing the logic, But it fails for some of tests like below, please check and rectify it.
1. [ 20, 18, 19, 3, 6, 7, 8] - returned value is 20 but expected 19
2. And what if all elements in list are equal, like [5, 5, 5, 5, 5]

[Cloudxxx]

why add 0 next to list2? and what happened to list1 as parameter in function ret_snd_largVal?

[Svithasisters]

by using if elif/else have to find 2nd largest number among 4 numbers . can u help me how to write pls.