mpld3: Object of type Timestamp is not JSON serialisable - matplotlib

Question

I am trying to produce an html file of a graph.
The following code works:
fig=plt.figure(figsize=(18.5,10))
for i in range(len(gl)):
plt.plot(rdfl[i]['datetime'], rdfl[i]['depth']*100, label=gl[i])
continue
plt.title(f'Stream levels (cm) in period {fdate} to {tdate}', y=1.0,)
plt.ylabel('Stream Depth (cm)', rotation=90)
plt.xlabel('Datetime')
plt.xticks(rotation=90)
plt.legend(title='Site',bbox_to_anchor=(1,1), loc="upper left", fontsize=10, title_fontsize=12)
plt.ion()
plt.draw()
#plt.show()
plt.pause(0.1)
html_str = mpld3.fig_to_html(fig)
Html_file= open(xdir1+"river_levels.html","w")
Html_file.write(html_str)
Html_file.close()
This code, however, does not :
fig2, ax1=plt.subplots()
bmtdf['mid_time']=pd.to_datetime(bmtdf['mid_time'],format = '%Y-%m-%d %H:%M:%S')
ax1.set_ylim(0,150)
ax1.stairs(bdf2['br_open_total'], bdfarr2['time'], label='Bresser/open')
ax1.scatter(bmtdf.mid_time, bmtdf.ic_amt, label='ic', marker='.')
ax1.scatter(bmtdf.mid_time, bmtdf.mc_amt, label='mc', marker='x')
ax1.scatter(bmtdf.mid_time, bmtdf.imd_amt, label='imd', marker='+')
ax1.scatter(bmtdf.mid_time, bmtdf.md_amt, label='md', marker='*')
ax1.scatter(bmtdf.mid_time, bmtdf.oak_amt, label='oak', marker='1')
ax1.scatter(bmtdf.mid_time, bmtdf.br_open_total, marker='')
ax1.legend(title='Forest Type', loc='upper left')
bmtdf.loc[[0],'br_open_total']=0
bmtdf[['mid_time','br_open_total', 'event_number']].apply(lambda row :ax1.text(*row), axis=1)
ax1.set_ylabel('Rain (mm)', rotation=90)
ax1.set_xlabel('Datetime')
ax2=ax1.twinx()
ax2.set_ylim(-250,250)
ax2.set_ylabel('Stream depth (cm)', rotation=90)
#ax2.set_yticks(np.arrange(0,1.8, 0.2))
for i in range(len(gl)):
ax2.plot(rdfl[i]['datetime'], rdfl[i]['depth']*100, label=gl[i])
continue
plt.xticks(rotation=90)
plt.legend(title='Stream', loc='upper right')
plt.title(f'Rain events, river levels and interception values in period {fdate} to {tdate}',y=1.0, pad=-24)
figManager = plt.get_current_fig_manager()
figManager.window.showMaximized()
fig2.canvas.manager.window.move(-1900,0)
plt.ion()
#plt.show()
plt.draw()
plt.pause(0.1)
plt.savefig(str(dirpath4+f'\\Bresser_open_plot_{fdate}-{tdate}.png'), bbox_inches='tight')
html_str = mpld3.fig_to_html(fig2)
Html_file= open(dirpath5+"bresser/open.html","w")
Html_file.write(html_str)
Html_file.close()
The second code block throws the error:
Traceback (most recent call last):
File "C:\Users\mtc20tfq\AppData\Local\Temp\ipykernel_21372\3088159653.py", line 1, in <cell line: 1>
html_str = mpld3.fig_to_html(fig2)
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\site-packages\mpld3\_display.py", line 261, in fig_to_html
figure_json=json.dumps(figure_json, cls=NumpyEncoder),
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\json\__init__.py", line 234, in dumps
return cls(
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\json\encoder.py", line 199, in encode
chunks = self.iterencode(o, _one_shot=True)
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\json\encoder.py", line 257, in iterencode
return _iterencode(o, 0)
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\site-packages\mpld3\_display.py", line 143, in default
return json.JSONEncoder.default(self, obj)
File "C:\ProgramData\Anaconda3\envs\spyder-env\lib\json\encoder.py", line 179, in default
raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type Timestamp is not JSON serializable
The 'time' variables that are plotted are:
type(rdfl[i]['datetime'][0])
Out[5]: pandas._libs.tslibs.timestamps.Timestamp
type(bdfarr2['time'][5])
Out[6]: pandas._libs.tslibs.timestamps.Timestamp
type(bmtdf['mid_time'][5])
Out[7]: pandas._libs.tslibs.timestamps.Timestamp
running
fig2, ax1=plt.subplots()
bmtdf['mid_time']=pd.to_datetime(bmtdf['mid_time'],format = '%Y-%m-%d %H:%M:%S')
ax1.set_ylim(0,150)
ax1.stairs(bdf2['br_open_total'], bdfarr2['time'], label='Bresser/open')
# ax1.scatter(bmtdf.mid_time, bmtdf.ic_amt, label='ic', marker='.')
# ax1.scatter(bmtdf.mid_time, bmtdf.mc_amt, label='mc', marker='x')
# ax1.scatter(bmtdf.mid_time, bmtdf.imd_amt, label='imd', marker='+')
# ax1.scatter(bmtdf.mid_time, bmtdf.md_amt, label='md', marker='*')
# ax1.scatter(bmtdf.mid_time, bmtdf.oak_amt, label='oak', marker='1')
# ax1.scatter(bmtdf.mid_time, bmtdf.br_open_total, marker='')
# ax1.legend(title='Forest Type', loc='upper left')
# bmtdf.loc[[0],'br_open_total']=0
# bmtdf[['mid_time','br_open_total', 'event_number']].apply(lambda row :ax1.text(*row), axis=1)
# ax1.set_ylabel('Rain (mm)', rotation=90)
# ax1.set_xlabel('Datetime')
ax2=ax1.twinx()
ax2.set_ylim(-250,250)
ax2.set_ylabel('Stream depth (cm)', rotation=90)
#ax2.set_yticks(np.arrange(0,1.8, 0.2))
for i in range(len(gl)):
ax2.plot(rdfl[i]['datetime'], rdfl[i]['depth']*100, label=gl[i])
continue
plt.xticks(rotation=90)
plt.legend(title='Stream', loc='upper right')
plt.title(f'Rain events, river levels and interception values in period {fdate} to {tdate}',y=1.0, pad=-24)
figManager = plt.get_current_fig_manager()
figManager.window.showMaximized()
fig2.canvas.manager.window.move(-1900,0)
plt.ion()
#plt.show()
plt.draw()
plt.pause(0.1)
plt.savefig(str(dirpath4+f'\\Bresser_open_plot_{fdate}-{tdate}.png'), bbox_inches='tight')
html_str = mpld3.fig_to_html(fig2)
Html_file= open(dirpath5+"\\bresser_open.html","w")
Html_file.write(html_str)
Html_file.close()
produces the plot in spyder, with the stairs plot visible , but it is not visible on the html plot.
It would seem that the .scatter lines are the ones where mpld3 refuses to serialise the Timestamp objects as it is only when these lines are run that the error appears.
Any suggestions would be greatly appreciated!
Edit: changed the ax1.scatter.... lines to:
ax1.scatter(bmtdf['mid_time'], bmtdf['ic_amt'], label='ic', marker='.')
ax1.scatter(bmtdf['mid_time'], bmtdf['mc_amt'], label='mc', marker='x')
ax1.scatter(bmtdf['mid_time'], bmtdf['imd_amt'], label='imd', marker='+')
ax1.scatter(bmtdf['mid_time'], bmtdf['md_amt'], label='md', marker='*')
ax1.scatter(bmtdf['mid_time'], bmtdf['oak_amt'], label='oak', marker='1')
ax1.scatter(bmtdf['mid_time'], bmtdf['br_open_total'], marker='')
but this makes no difference