Exporting a matplotlib chart directly to Excel? Without saving to file first

Question

I am trying to write a matplotlib image directly into an Excel file using xlsx writer - ideally without saving the file to the disk.

I have found this answer: Writing pandas/matplotlib image directly into XLSX file but I cannot get it to work, especially not with Python 3.

This: wks1.insert_image(2,2, imgdata doesn't work, because:

path should be string, bytes, os.PathLike or integer, not _io.BytesIO

This: wks1.insert_image(2,2,"",{'image data': imgdata}) gives a warning

Image file '' not found.

and produces an excel file with no chart.

What does work is saving the file locally - but I'd like to understand if there's a way to avoid it.

fig.savefig('test.png', format='png')
wks1.insert_image(2,2, 'test.png')

Thoughts? The full code is:

import xlsxwriter
import numpy as np
import matplotlib.pyplot as plt
import io

x=np.linspace(-10,10,100)
y=x**2

fig,ax=plt.subplots()
ax.plot(x,y)

workbook = xlsxwriter.Workbook('test chart.xlsx')
wks1=workbook.add_worksheet('Test chart')
wks1.write(0,0,'test')

imgdata=io.BytesIO()
fig.savefig(imgdata, format='png')

wks1.insert_image(2,2,"",{'image data': imgdata})
#wks1.insert_image(2,2, imgdata)

workbook.close()

Answer 1

According to the documentation (and the link to the question you provided), the correct spelling for the optional argument to be passed to insert_image is image_data (noting the underscore _)

import xlsxwriter
import numpy as np
import matplotlib.pyplot as plt
import io

x=np.linspace(-10,10,100)
y=x**2

fig,ax=plt.subplots()
ax.plot(x,y)

workbook = xlsxwriter.Workbook('test chart.xlsx')
wks1=workbook.add_worksheet('Test chart')
wks1.write(0,0,'test')

imgdata=io.BytesIO()
fig.savefig(imgdata, format='png')
wks1.insert_image(2,2, '', {'image_data': imgdata})

workbook.close()