Спасибо Roman_N, вот мой код:
import pandas as pd
import xlrd
import functools, operator
import itertools
from collections import Counter
df = pd.read_csv("BN.csv")
result = []
for index,row in df.iterrows():
s = [[row['a1'],row['a2']], [row['b1'],row['b2']], [row['c1'],row['c2']], [row['d1'],row['d2']]]
for item in list(itertools.product(*s)):
result.append(item)
# print(result)
counts = Counter(item for item in result)
for element in counts:
print(element, counts[element])
print(list, 'length is', len(counts))