Hi Alejandro:
Below Code Update One Product using Odoo XMLRPC you can change product_id and file_path

import base64
# Odoo API authentication

product_id=13
file_path = "/home/Estain/Documents/example.jpg"
with open(file_path, 'rb') as f:
    	​data = f.read()
    	​img = base64.b64encode
    	​encoded_image_data = base64.b64encode(data)
    	​ImageSend = encoded_image_data.decode('ascii')
	​# Update product record with new image
	​product = models.execute_kw(db, uid, password, 'product.template', 'write', [[product_id], 	​{'image_1920': ImageSend,}])

Hi Alejandro: You can try using python's base64 module to encode the content and pass it to the api.