couple of potential solutions
from urllib.parse import quote
import requests
url = 'https://your_dall_e_url_with_%2B'
encoded_url = quote(url, safe='')
# safe='' ensures that all characters are encoded
# Now use encoded_url for your post request
requests.post(encoded_url)
or maybe
url = 'https://your_dall_e_url_with_%2B'
url = url.replace('%2B', '%252B') # URL encode the '+' character only
# Now use the new URL for your post request
requests.post(url)