Writing table to memory in ArcPy gives ERROR 000354

Currently I try to improve an ArcPy script which is run outside ArcGIS Pro 2.5 in Spyder.

I want to write a table to memory using the Table to Table tool. This tool is placed inside a loop and writes a new table to my workspace for every run.

Part of my code:

#Defining output path
output = "Routebestand_portaal_"+str(nummer_portaal)+"_selectie"
portalen_join_met_totaal = arcpy.AddJoin_management(in_layer_or_view="Routebestand_200605_totaalbestand_opgeschoond_copy",
                                                in_field="Portal_OBJECTID", join_table=Portaal_vultabel,
                                                join_field="Portal_OBJECTID", join_type="KEEP_COMMON")[0]

Portaal_vultabel = r"C:UsersWorkPortalen_met_intensiteit"

#Write table to gdb
arcpy.TableToTable_conversion(in_rows=portalen_join_met_totaal, out_name= output, where_clause="", field_mapping="Van___naar "Van___naar" true true false 200 Text 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Van___naar,0,200;VTGKM_VWH "VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.VTGKM_VWH,-1,-1;Portal_OBJECTID "Portal_OBJECTID" true true false 4 Long 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Portal_OBJECTID,-1,-1;SUM_VTGKM_TOT "SUM_VTGKM_TOT" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_TOT,-1,-1;SUM_VTGKM_VWH "SUM_VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_VWH,-1,-1", config_keyword="")[0]

..this code works and writes the table to my workspace. Now I want to write the table to memory.

---

My first approach was figure out how to write a table to memory outside a loop and without considering the variable output:

#Approach1  - using 'memory'
output1 = r"memorytmpTable"     
portalen_join_met_totaal = arcpy.AddJoin_management(in_layer_or_view="Routebestand_200605_totaalbestand_opgeschoond_copy",
                                                in_field="Portal_OBJECTID", join_table=Portaal_vultabel,
                                                join_field="Portal_OBJECTID", join_type="KEEP_COMMON")[0]

Portaal_vultabel = r"C:UsersWorkPortalen_met_intensiteit"           

arcpy.TableToTable_conversion(in_rows=portalen_join_met_totaal, out_name= output1, where_clause="", field_mapping="Van___naar "Van___naar" true true false 200 Text 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Van___naar,0,200;VTGKM_VWH "VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.VTGKM_VWH,-1,-1;Portal_OBJECTID "Portal_OBJECTID" true true false 4 Long 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Portal_OBJECTID,-1,-1;SUM_VTGKM_TOT "SUM_VTGKM_TOT" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_TOT,-1,-1;SUM_VTGKM_VWH "SUM_VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_VWH,-1,-1", config_keyword="")[0]

..or these lines:

#Approach2 - using 'in_memory'
output2 = r"in_memorytmpTable"
portalen_join_met_totaal = arcpy.AddJoin_management(in_layer_or_view="Routebestand_200605_totaalbestand_opgeschoond_copy",
                                                in_field="Portal_OBJECTID", join_table=Portaal_vultabel,
                                                join_field="Portal_OBJECTID", join_type="KEEP_COMMON")[0]

Portaal_vultabel = r"C:UsersWorkPortalen_met_intensiteit"

arcpy.TableToTable_conversion(in_rows=portalen_join_met_totaal, out_name= output2, where_clause="", field_mapping="Van___naar "Van___naar" true true false 200 Text 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Van___naar,0,200;VTGKM_VWH "VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.VTGKM_VWH,-1,-1;Portal_OBJECTID "Portal_OBJECTID" true true false 4 Long 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Routebestand_200605_totaalbestand_opgeschoond_copy.Portal_OBJECTID,-1,-1;SUM_VTGKM_TOT "SUM_VTGKM_TOT" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_TOT,-1,-1;SUM_VTGKM_VWH "SUM_VTGKM_VWH" true true false 8 Double 0 0,First,#,C:UsersWorkData.gdbRoutebestand_200605_totaalbestand_opgeschoond_copy,Portalen_met_intensiteit.SUM_VTGKM_VWH,-1,-1", config_keyword="")[0]

..both the options delivered an error message:

ExecuteError: Failed to execute. Parameters are not valid.
ERROR 000354: The name contains invalid characters
Failed to execute (TableToTable).

What I would like to get is something like r"memory + "Routebestand_portaal_" + str(nummer_portaal) + "_selectie"

Any suggestions how to solve this?

arcpy.TableToTable_conversion("vegtable.dbf", "memory", "vegtable")

# output2 = just the output name, not the path
arcpy.TableToTable_conversion(in_rows=portalen_join_met_totaal, out_path="memory", out_name= output2, where_clause="", ......