Convert COBOL to Python

Conversion Samples of COBOL to Python

Ispirer Toolkit analyzes all object dependencies during the conversion process and provides not only line-by-line conversion, but resolves type conversions as well. The software understands and transforms the necessary inheritance dependencies. It parses the entire source code, builds an internal tree with all the information about the objects, and uses it in the migration process.

To convert structures, we have implemented additional type conversion classes to store variable sizes to convert redefines and arrays so that they work similar to COBOL logic.

The code samples below provide you with more details.

• Common variables declaration structure conversion:

  COBOL

   
  01 varlnk.
    05 varlnk-1 PIC 999.
    05 varlnk-2 PIC X(10).
    05 varlnk-3 PIC 9(7).
   

  → Python

   
  Varlnk = VarlnkType()
   
  class VarlnkType(Record): 
      Varlnk_1 = None
      Varlnk_2 = None
      Varlnk_3 = None
      def __init__(self): 
          self.Varlnk_1 = IntField(3)
          self.Varlnk_2 = StrField(10)
          self.Varlnk_3 = IntField(7)
          super().__init__()              

• Common REDEFINES conversion:

  COBOL

   
  01 var1 PIC XXX  VALUE '111'.
  01 var2 REDEFINES var1.
    05  vvv1  PIC 9.
    05  vvv2  PIC 99.
   

  → Python

   
  Var1 = StrField(3,'111')
  Var2 = Var2Type()
   
  Var2.Redefine(Var1);
   
  class Var2Type(Record): 
      Vvv1 = None
      Vvv2 = None
      def __init__(self): 
          self.Vvv1 = IntField(1)
          self.Vvv2 = IntField(2)
          super().__init__()
   

• Common array conversion:

  COBOL

   
  01 var5.
     05 var5-occurs OCCURS 2 TIMES.
        10 var5-occurs-txt PIC X(6) VALUE ' TEXT1'.
   

  → Python

   
  Var5 = Var5Type()
   
  class Var5OccursType(Record): 
      Var5OccursTxt = None
      def __init__(self): 
          self.Var5OccursTxt = StrField(6,' TEXT1')
          super().__init__()
   
   
  class Var5Type(Record): 
      Var5Occurs =[]
      def __init__(self): 
          for i in range(1,2): 
              obj = Var5OccursType()
              self.Var5Occurs = self.Var5Occurs+[obj]
   
          super().__init__()
   

• COBOL call chain with PERFORMs conversion:

  COBOL

   
  TopLevel.
      DISPLAY "In TopLevel. Starting to run program"
      PERFORM OneLevelDown
      DISPLAY "Back in TopLevel.".
      STOP RUN.
   
  OneLevelDown.
      DISPLAY ">>>> Now in OneLevelDown"
      PERFORM TwoLevelsDown
      DISPLAY ">>>> Back in OneLevelDown".
   
  TwoLevelsDown.
      DISPLAY ">>>>>>>> Now in TwoLevelsDown."
      PERFORM ThreeLevelsDown.
      DISPLAY ">>>>>>>> Back in TwoLevelsDown.".
   
  ThreeLevelsDown.
      DISPLAY ">>>>>>>>>>>> Now in ThreeLevelsDown".
   

  → Python

   
  class CobSmplCbl: 
      CobSmplCblCompatibility = None
      def __new__(cls): 
          if not hasattr(cls,'instance'): 
              cls.instance = super(CobSmplCbl,cls).__new__(cls)
          return cls.instance  
   
      def __init__(self): 
          self.CobSmplCblCompatibility = Compatibility()
          self.CobSmplCblCompatibility.GetAllMethods(self)
          self.CobSmplCblProcedureDivision()  
   
      def CobSmplCblProcedureDivision(self): 
          self.CobSmplCblCompatibility.InitializeMethodsQueue()
          self.CobSmplCblCompatibility.CallNextMethod(self,True)  
   
      def Toplevel(self): 
          print("In TopLevel. Starting to run program")
          self.CobSmplCblCompatibility.PerformThru(self,"Oneleveldown")
          print("Back in TopLevel.")
          exit()
          self.CobSmplCblCompatibility.CallNextMethod(self,True)
   
      def Oneleveldown(self): 
          print(">>>> Now in OneLevelDown")
          self.CobSmplCblCompatibility.PerformThru(self,"Twolevelsdown")
          print(">>>> Back in OneLevelDown")
          self.CobSmplCblCompatibility.CallNextMethod(self,True)
   
      def Twolevelsdown(self): 
          print(">>>>>>>> Now in TwoLevelsDown.")
          self.CobSmplCblCompatibility.PerformThru(self,"Threelevelsdown")
          print(">>>>>>>> Back in TwoLevelsDown.")
          self.CobSmplCblCompatibility.CallNextMethod(self,True)
   
      def Threelevelsdown(self): 
          print(">>>>>>>>>>>> Now in ThreeLevelsDown")
          self.CobSmplCblCompatibility.CallNextMethod(self,True)
   

Copy statement conversion

During the conversion stage, the code from the copy files is included in the program and replaced with the appropriate copy statements, thereafter the program converts the entire code.

• If statement conversion:

  COBOL

   
    if  var3 = var4
        move "D" to var3
    else
        move " " to var3.
   

  → Python

   
          if Var3.Value == Var4.Value: 
              Var1.Value = "D"
          else: 
              Var3.Value = " "
   

• PERFORM UNTIL statement conversion:

  COBOL

   
    PERFORM UNTIL IterCount = 5
       ADD 1 TO IterCount
    END-PERFORM
   

  → Python

   
          while (not(Itercount == 5)): 
              Itercount += 1