将索引转换为切片或整数：“类型错误：列表索引必须是整数或切片，而不是 str”

Question

我已经从我的数据框 (df1) 创建了列表，我正在尝试减去值（高潮和低潮）并绘制它们，但一直卡在最大值上。这是我的代码：

import pandas as pd
import numpy as np
df1 = pd.read_csv (r'C:\Intel\Solinst-cleaned up\yellow.csv', skiprows = 13, encoding= 'unicode_escape', parse_dates=[['Date', 'Time']])

# Normal condition (From Jan 20th to Feb 11th)
start = 50     # First row to consider
stop = 3200     # Last row to consider
interval = 75  # The desired chunk size
x=df1['Date_Time'][50:125]

y1=[]
for i in range(start, stop, interval):
    y1.append(df1["Mlevel"][i:(i + interval)])
    
#y1 = y1.reset_index(drop=True)

hightide=[]   
for i in range(start, stop, interval):
    hightide=max(y1[1].loc[y1['Mlevel'][i:(i + interval)]])

我得到：

  File "C:/Users/mr179/Desktop/Research/PhD/codes/test.py", line 42, in <module>
    hightide=max(y1[1].loc[y1['Mlevel'][i:(i + interval)]])

TypeError: list indices must be integers or slices, not str

y1 看起来像这样：