How do I write R like for-loops in Python with indexing and many ifelse statements in pandas dataframes?

Question

I have a specific for loop which I want to translate into Python but realized that Python does not use indexing. I know how to use enumerate() and simpler for loops where there is no deeper purpose with the for loop.

This time, I have a grouped dataframe which needs to iterate from index 2:N and thereby skipping 1st index in R => 0th index in Python.

Basically, I want to look for product number and store number occuring in row i to see if it matches row i-1 and then execute some ifelse statements with values occurring in row i and i-1 from columns in the dataframe.

For loop in R using data.table set() that I want to translate into Python

for(i in 2:nrow(df)) set(df, i, "col_A", 
                         ifelse(df$col_B[i]==df$col_B[i-1] & df$col_C[i]==df$col_C[i-1],
                                0, 
                                1
                                )
                         )