def detect_outliers(df, columns):
outlier_indices = []
for c in columns:
# 1st quartile
q1 = np.percentile(df[c], 25)
# 3rd quqartile
q3 = np.percentile(df[c], 75)
… outlier_indices.extend(outlier_list_col)
outlier_indices = Counter(outlier_indices)
multiple_outlier = list(i for i,v in outlier_indices.items() if v > 2)
return multiple_outlier