“Line2D”对象没有属性“标签”； matplotlib 图表中的水平线将不会使用 axhline pycharm 3.9 到 3.10 开关显示

Question

我升级到了一台新电脑，并将版本从 3.9 切换到了 3.10。由于错误，我现在无法使用完全相同的代码：“Line2D”对象没有属性“Label”。我已经解决了几个小时的问题，但没有任何进展。我注释掉了 axhline 和图例（第 53、54 行），代码运行并显示绘图，但当然我的水平线现在消失了。

'import pandas as pd
from matplotlib import pyplot as plt
from matplotlib import dates as mpl_dates
from matplotlib.lines import Line2D # for making the custom legend (line 87)
import matplotlib.ticker as ticker
from matplotlib import legend

from pylab import rcParams 
rcParams['figure.figsize'] = 8, 6

plt.style.use('fast')

@ticker.FuncFormatter
def major_formatter(x, pos):
    label = str(-x) if x < 0 else str(x)
    return label

Stage= pd.read_csv('GRL_Stage_2021.csv')
Stage['OBS DATE'] = pd.to_datetime(Stage['OBS DATE'])
Stage.sort_values('OBS DATE', inplace=True)
fig = plt.figure()

Rain= pd.read_csv('FlowData_2021_WY.csv')

x= Stage['OBS DATE']
y= Stage['BTC_HF']
y2=Stage['DES_DPI']

fig,ax= plt.subplots() #needed for creating .ax type (defined axes)
ax2=ax.twinx() # for the second Y axis

ax2.yaxis.set_major_formatter(major_formatter)# this relates to the formatter at the top

ax.plot(x,y, color= 'blue', markersize='2', linewidth= '2', label='Sacramento R. @ Butte 
City')
ax2.bar(x,y2, color='grey', alpha= .85, width=.6, label= 'Rain(in)')

y_val2= 80000 # monitor stage

#ax.axhline(y=y_val2, color = 'chartreuse', zorder=0, linestyle= '--', Label = 'Monitor 
#Stage 80k CFS')                 ******lines 53,54******
#plt.legend(fontsize='small')

ax.fill_between(x, y, color= 'darkseagreen', alpha= .75)
ax.legend(loc='center', bbox_to_anchor=(0.18, 0.82),fontsize='small')
ax2.legend(loc='center', bbox_to_anchor=(0.1, 0.83), fontsize='small') #bbox is x,y location 
of legend

ax.set_xlabel('Date')
ax.set_ylabel('River Flow (CFS)')
ax2.set_ylabel('Daily Rain Totals (In.)')
ax.set_title('Sacramento River (Butte City) Observed Daily Flow and Rain Totals')
fig.patch.set_facecolor('skyblue')
plt.gcf().autofmt_xdate()

date_format = mpl_dates.DateFormatter('%b, %d')
plt.gca().xaxis.set_major_formatter(date_format)

print(plt.style.available)
plt.tight_layout()
ax.margins(x=0) 
ax.set_ylim(ymin=0)  
print(plt.style.available)

custom_lines = [Line2D([0], [0], color='magenta', alpha=.75, lw=2, linestyle='--'),
                Line2D([0], [0], color='chartreuse', alpha=.75, lw=2, linestyle= '--'),]

ax.legend(custom_lines, ['Levee/Channel Overflow (160k CFS)', 'Flood Risk Warning! (80k 
CFS)'],facecolor='yellow',
          fontsize='small',loc='center', bbox_to_anchor=(0.42, 0.68),)'
plt.show()

回溯（最近一次调用最后一次）： 文件“C:\Users\rgreat\PycharmProjects\pythonProject\pythonProject\BTC WxFig.py”，第 53 行，位于 ax.axhline(y=y_val2, color = 'chartreuse', zorder=0, linestyle= '--', Label = '监控阶段 80k CFS') 文件“C:\Users\rgreat\AppData\Local\Programs\Python\Python310\lib\site-packages\matplotlib\axes_axes.py”，第 737 行，位于 axhline l = mlines.Line2D([xmin, xmax], [y, y], 变换=trans, **kwargs) 文件“C:\Users\rgreat\AppData\Local\Programs\Python\Python310\lib\site-packages\matplotlib\lines.py”，第 393 行，在 init 中 自我更新（kwargs） 文件“C:\Users\rgreat\AppData\Local\Programs\Python\Python310\lib\site-packages\matplotlib\artist.py”，第 1064 行，更新中 引发 AttributeError(f"{type(self).name!r} object " AttributeError：“Line2D”对象没有属性“Label”