使用python查找非null的最小值

I have used min(A,B,C,D) in python. This works perfectly in finding the lowest value, however, if I have a null value (0 value) in any of the varaibles A,B,C or D, it would return the null value (or 0). Any ideas how to return the non-null or non-zero value in my case? thanksI have used min(A,B,C,D) in python. This works