python中pd.cut()函数用法的问题，里面的bins……

想给我的excel数据作分类标记，单个fibercoose这个定义的函数能够正常运行，但是嵌入函数中却不能正常运行，报错了。
显示 ValueError: bins must increase monotonically.

请问这是什么问题呢？
该如何解决？感谢！！

import pandas as pd
from pandas import read_excel
import os
path = r"C:/Users/74458/Desktop/11/"


def fiberchoose(fp,file):
    writer = pd.ExcelWriter(path + '1' + file + '.xlsx')
    df = pd.DataFrame(pd.read_excel(fp))
    bins = [min(df.纵)-1, 100, 150, 190, 245, 290, 330, max(df.纵)+1]
    lab = ['1', '2', '3', '4', '5', '6', '7']
    df['demo'] = pd.cut(df.纵, bins, right=True, labels=lab)
    df.to_excel(writer, file, index=False)  # demo.to_excel(writer,'0.1',index=False) 这样会导致只把demo存入excel
    writer.save()
    print('处理完',file)


def getfiles():
    files = os.listdir(path)
    for file in files:
        fp = path + file
        fiberchoose(fp,file)

if __name__ == '__main__':
    getfiles()
    print("处理完毕，按回车键结束程序。")