Accessing fields info from code block using Python Parser of Calculate Field in script?

Question

I need to codify a field with other fields information I have this code running into a script:

            # Process: Calculate Field (12)
  arcpy.CalculateField_management(RedHID_Layer, "TIPOcorr", "cadena", "VB", "cadena = \"\"\\nif (Not "
                                                                                  "isNull ([ACC])) "
                                                                                  "Then\\ncadena = [ACC]\\nend "
                                                                                  "if\\n\\nif (Not isNull (["
                                                                                  "EDIF])) Then\\n   if cadena "
                                                                                  "= \"\" then\\n     cadena = "
                                                                                  " [EDIF]\\n   else\\n     "
                                                                                  "cadena = cadena & \", "
                                                                                  "\" & [EDIF]\\n   end "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([MAGS])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [MAGS]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [MAGS]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([OBS1])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [OBS1]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [OBS1]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([OBS2])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [OBS2]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [OBS2]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([REM1])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [REM1]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [REM1]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([REM2])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [REM2]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [REM2]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([REM3])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [REM3]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [REM3]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([QMD1])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [QMD1]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [QMD1]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([QMD2])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [QMD2]\\n  "
                                                                                  "else\\n   cadena = cadena & "
                                                                                  "\", \" & [QMD2]\\nend "
                                                                                  "if\\nend if\\n\\nif (Not "
                                                                                  "isNull ([RJT])) Then\\n   "
                                                                                  "if cadena = \"\" then\\n   "
                                                                                  "cadena =  [RJT]\\n  else\\n "
                                                                                  "  cadena = cadena & \", "
                                                                                  "\" & [RJT]\\nend if\\nend "
                                                                                  "if\\n")

This is in vb and I need it in Python, so I wrote this:

            arcpy.CalculateField_management(in_table=RedHID_Layer, field="TIPOcorr", expression='cadena',
                                        expression_type="PYTHON",
                                        code_block='cadena = ""\nif "!ACC!" is not None:\n    cadena = "!ACC!"\n\nif "!EDIF!":\n    if cadena == "":\n        cadena = "!EDIF!"\n    else:\n        cadena = cadena + ", " + "!EDIF!"\n\nif "!MAGS!":\n    if cadena == "":\n        cadena = "!MAGS!"\n    else:\n        cadena = cadena + ", " + "!MAGS!"\n\nif "!OBS1!":\n    if cadena == "":\n        cadena = "!OBS1!"\n    else:\n        cadena = cadena + ", " + "!OBS1!"\n\nif "!OBS2!":\n    if cadena == "":\n        cadena = "!OBS2!"\n    else:\n        cadena = cadena + ", " + "!OBS2!"\n\nif "!REM1!":\n    if cadena == "":\n        cadena = "!REM1!"\n    else:\n        cadena = cadena + ", " + "!REM1!"\n\nif "!REM2!":\n    if cadena == "":\n        cadena = "!REM2!"\n    else:\n        cadena = cadena + ", " + "!REM2!"\n\nif "!REM3!":\n    if cadena == "":\n        cadena = "!REM3!"\n    else:\n        cadena = cadena + ", " + "!REM3!"\n\nif "!QMD1!":\n    if cadena == "":\n        cadena = "!QMD1!"\n    else:\n        cadena = cadena + ", " + "!QMD1!"\n\nif "!QMD2!":\n    if cadena == "":\n        cadena = "!QMD2!"\n    else:\n        cadena = cadena + ", " + "!QMD2!"\n\nif "!RJT!":\n    if cadena == "":\n        cadena = "!RJT!"\n    else:\n        cadena = cadena + ", " + "!RJT!"\n')

But still don't works. The result may be:

Answer 1

It looks like you've converted this to a python 'script' from model builder...while that produces functional Python, it's pretty ugly.

It looks like your original VBA codeblock is something like:

cadena = ""

if (Not isNull ([ACC])) Then 
    cadena = [ACC]
end if

if (Not isNull ([EDIF])) Then
    if cadena = "" then
        cadena = [EDIF]
    else
        cadena = cadena & ", " & [EDIF]
    end if
end if

if (Not isNull ([MAGS])) Then
    if cadena = "" then
        cadena =  [MAGS]
    else
        cadena = cadena & ", " & [MAGS]
    end if
end if
...

And, it looks like you've tried to do a similar pattern in Python like this:

cadena = ""
if "!ACC!" is not None:
    cadena = "!ACC!"

if "!EDIF!":
    if cadena == "":
            cadena = "!EDIF!"
    else:
            cadena = cadena + ", " + "!EDIF!"

if "!MAGS!":
    if cadena == "":
            cadena = "!MAGS!"
    else:
            cadena = cadena + ", " + "!MAGS!"
...

A quick fix should be to remove the quotes (") from around the fields: ie. !ACC! instead of "!ACC!".

I would recommend something more Pythonic, though:

cadena = ', '.join([x for x in [!ACC!,!EDIF!,!MAGS!,!OBS1!,!OBS2!,!REM1!,!REM2!,
                                 !REM3!,!QMD1!,!QMD2!,!RJT!] if x is not None])