water.py

from bs4 import BeautifulSoup
import requests
import re

requested_data = [ "Calcium" ]

post_data = {
  "methode": "rechercher",
  "idRegion": "73",
  "usd": "AEP",
  "posPLV": "0",
  "departement": "031",
  "communeDepartement": "555",
  "reseau": "000006_031"
}

http_session = requests.session()

first_url = "https://orobnat.sante.gouv.fr/orobnat/afficherPage.do?methode=menu&idRegion={region}&dpt={dpt}&usd={usd}&comDpt={comdpt}".format( region=post_data["idRegion"], dpt=post_data["departement"], usd=post_data["usd"], comdpt=post_data["communeDepartement"] )

print( "Loading:", first_url )
result = http_session.get( first_url )

if result.status_code == 200:
  failure = False
  pos_plv = 0
  source_url = "https://orobnat.sante.gouv.fr/orobnat/rechercherResultatQualite.do"

  pattern = re.compile( r"{0}".format( requested_data[0] ) )
  
  while pattern.search( result.text ) is None:

    print( "Try #{0}".format( pos_plv ) )
    print( "Loading:", source_url )
    result = http_session.post( source_url, post_data )

    if result.status_code != 200:
      print( "Unable to get page:", result.status_code, result.reason )
      failure = True
      break
    
    pos_plv += 1
    post_data["posPLV"] = str(pos_plv)
    
  if not failure:
    print( "Data found." )

    soup = BeautifulSoup( result.text )
    
    # All page tables have the same "id"...
    for table in soup.find_all( id="tableau" ):
      tds = table.find_all( "td", { "class": "gras" } )
      found = False
      
      for td in tds:
        if len(td.contents):
          # Some td have div tag inside...
          title = td.contents[0].find( "Valeur" )

          if title is not None and title >= 0:
            # Good table !
            found = True
            break
      
      if found:
        for tr in table.find_all( "tr" ):
          td = tr.find( "td" )
          needed_data = False

          for value in requested_data:
            if len(td.contents) and td.contents[0].find( value ) >= 0:
              needed_data = True
              break
          
          if needed_data:
            print( " ".join( tr.stripped_strings ) )

  else:
    print( "Unable to find criteria" )

else:
  print( "Can not get main page:", result.status_code, result.reason )