示例：
# -*- coding:utf-8 -*-
import pandas as pd # 需要安装 pandas
# 读取 Excel 文件
xlsxfile = '汇总班级名单.xlsx'
df = pd.read_excel('./excel_files/'+xlsxfile, dtype={'班级': str})
# df = pd.read_excel('example.xlsx', sheet_name='Sheet1') # 指定表名
banji = df['班级']
maxbj = len(set(banji)) # 常用
maxbj = len(banji.unique())
maxbj = len({}.fromkeys(banji).keys())
maxbj = pd.Series(banji).value_counts().size # 最快
print(maxbj)详细分析：链接地址