Combine two or more columns into a new column by row condition

Question

I would like to combine two or more columns into a new columns, based on the row condition ( which is 1, an integer ) the new columns should be a column contains joined string.<

Answer 1

This is one of the few things that a for loop would be appropriate for in pandas

col_names = rdf.columns.tolist()
rdf["NEW"] = ""

for col in col_names:
    rdf.loc[rdf[col] == 1, "NEW"] = rdf.loc[rdf[col] == 1, "NEW"] + ("," + col)

rdf["NEW"] = rdf["NEW"].str.strip(",")