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

  1. 01 varlnk.
  2.   05 varlnk-1 PIC 999.
  3.   05 varlnk-2 PIC X(10).
  4.   05 varlnk-3 PIC 9(7).

  → Python

  1. Varlnk = VarlnkType()
  2.  
  3. class VarlnkType(Record):
  4.     Varlnk_1 = None
  5.     Varlnk_2 = None
  6.     Varlnk_3 = None
  7.     def __init__(self):
  8.         self.Varlnk_1 = IntField(3)
  9.         self.Varlnk_2 = StrField(10)
  10.         self.Varlnk_3 = IntField(7)
  11.         super().__init__()

• Common REDEFINES conversion:

  COBOL

  1. 01 var1 PIC XXX  VALUE '111'.
  2. 01 var2 REDEFINES var1.
  3.   05  vvv1  PIC 9.
  4.   05  vvv2  PIC 99.

  → Python

  1. Var1 = StrField(3,'111')
  2. Var2 = Var2Type()
  3.  
  4. Var2.Redefine(Var1);
  5.  
  6. class Var2Type(Record):
  7.     Vvv1 = None
  8.     Vvv2 = None
  9.     def __init__(self):
  10.         self.Vvv1 = IntField(1)
  11.         self.Vvv2 = IntField(2)
  12.         super().__init__()

• Common array conversion:

  COBOL

  1. 01 var5.
  2.    05 var5-occurs OCCURS 2 TIMES.
  3.       10 var5-occurs-txt PIC X(6) VALUE ' TEXT1'.

  → Python

  1. Var5 = Var5Type()
  2.  
  3. class Var5OccursType(Record):
  4.     Var5OccursTxt = None
  5.     def __init__(self):
  6.         self.Var5OccursTxt = StrField(6,' TEXT1')
  7.         super().__init__()
  8.    
  9.  
  10. class Var5Type(Record):
  11.     Var5Occurs =[]
  12.     def __init__(self):
  13.         for i in range(1,2):
  14.             obj = Var5OccursType()
  15.             self.Var5Occurs = self.Var5Occurs+[obj]
  16.        
  17.         super().__init__()

• COBOL call chain with PERFORMs conversion:

  COBOL

  1. TopLevel.
  2.     DISPLAY "In TopLevel. Starting to run program"
  3.     PERFORM OneLevelDown
  4.     DISPLAY "Back in TopLevel.".
  5.     STOP RUN.
  6.  
  7. OneLevelDown.
  8.     DISPLAY ">>>> Now in OneLevelDown"
  9.     PERFORM TwoLevelsDown
  10.     DISPLAY ">>>> Back in OneLevelDown".
  11.  
  12. TwoLevelsDown.
  13.     DISPLAY ">>>>>>>> Now in TwoLevelsDown."
  14.     PERFORM ThreeLevelsDown.
  15.     DISPLAY ">>>>>>>> Back in TwoLevelsDown.".
  16.  
  17. ThreeLevelsDown.
  18.     DISPLAY ">>>>>>>>>>>> Now in ThreeLevelsDown".

  → Python

  1. class CobSmplCbl:
  2.     CobSmplCblCompatibility = None
  3.     def __new__(cls):
  4.         if not hasattr(cls,'instance'):
  5.             cls.instance = super(CobSmplCbl,cls).__new__(cls)
  6.         return cls.instance  
  7.  
  8.     def __init__(self):
  9.         self.CobSmplCblCompatibility = Compatibility()
  10.         self.CobSmplCblCompatibility.GetAllMethods(self)
  11.         self.CobSmplCblProcedureDivision()  
  12.  
  13.     def CobSmplCblProcedureDivision(self):
  14.         self.CobSmplCblCompatibility.InitializeMethodsQueue()
  15.         self.CobSmplCblCompatibility.CallNextMethod(self,True)  
  16.  
  17.     def Toplevel(self):
  18.         print("In TopLevel. Starting to run program")
  19.         self.CobSmplCblCompatibility.PerformThru(self,"Oneleveldown")
  20.         print("Back in TopLevel.")
  21.         exit()
  22.         self.CobSmplCblCompatibility.CallNextMethod(self,True)
  23.    
  24.     def Oneleveldown(self):
  25.         print(">>>> Now in OneLevelDown")
  26.         self.CobSmplCblCompatibility.PerformThru(self,"Twolevelsdown")
  27.         print(">>>> Back in OneLevelDown")
  28.         self.CobSmplCblCompatibility.CallNextMethod(self,True)
  29.  
  30.     def Twolevelsdown(self):
  31.         print(">>>>>>>> Now in TwoLevelsDown.")
  32.         self.CobSmplCblCompatibility.PerformThru(self,"Threelevelsdown")
  33.         print(">>>>>>>> Back in TwoLevelsDown.")
  34.         self.CobSmplCblCompatibility.CallNextMethod(self,True)
  35.    
  36.     def Threelevelsdown(self):
  37.         print(">>>>>>>>>>>> Now in ThreeLevelsDown")
  38.         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

  1. if  var3 = var4
  2.       move "D" to var3
  3.   else
  4.       move " " to var3.

  → Python

  1. if Var3.Value == Var4.Value:
  2.             Var1.Value = "D"
  3.         else:
  4.             Var3.Value = " "

• PERFORM UNTIL statement conversion:

  COBOL

  1. PERFORM UNTIL IterCount = 5
  2.      ADD 1 TO IterCount
  3.   END-PERFORM

  → Python

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