VBA GoTo & Error Handling to Python

Why GoTo Exists in VBA

VBA inherited GoTo from BASIC. It serves three common purposes in legacy code:

1. Error handling: On Error GoTo ErrHandler is VBA's only structured error mechanism.
2. Retry loops: Jumping back to a label after a failed operation.
3. Cleanup blocks: Jumping to a cleanup label before exiting a Sub.

Python has structured alternatives for all three — try/except, while loops, and try/finally.

Pattern 1: On Error GoTo → try/except

This is the most common GoTo pattern. VBA uses labels for error handlers; Python uses structured exception blocks.

Sub ProcessFile()
    On Error GoTo ErrHandler

    Open "data.txt" For Input As #1
    ' ... process file ...
    Close #1
    Exit Sub

ErrHandler:
    MsgBox "Error: " & Err.Description
    Close #1
End Sub

def process_file():
    try:
        with open("data.txt") as f:
            # ... process file ...
            pass
    except Exception as e:
        print(f"Error: {e}")

Python's with statement also replaces the need for explicit Closecalls — the file is closed automatically when the block exits, even if an exception occurs.

Pattern 2: On Error Resume Next → explicit try/except

On Error Resume Next silently ignores all errors and continues execution. This is dangerous because it hides bugs. In Python, handle specific expected errors explicitly.

Sub SafeRead()
    On Error Resume Next
    val = Cells(1, 1).Value
    x = CDbl(val)
    If Err.Number <> 0 Then
        x = 0
        Err.Clear
    End If
    On Error GoTo 0
End Sub

def safe_read(ws):
    val = ws.cell(row=1, column=1).value
    try:
        x = float(val)
    except (ValueError, TypeError):
        x = 0

Instead of suppressing all errors, Python catches only the specific exceptions you expect (ValueError, TypeError). Unexpected errors still propagate and surface immediately.

Pattern 3: GoTo Retry → while loop

Sub GetInput()
Retry:
    answer = InputBox("Enter a number:")
    If Not IsNumeric(answer) Then
        MsgBox "Invalid input"
        GoTo Retry
    End If
End Sub

def get_input():
    while True:
        answer = input("Enter a number:")
        try:
            float(answer)
            break
        except ValueError:
            print("Invalid input")

Any GoTo that jumps backward to a label is effectively a loop. Replace with while True and break when the condition is met.

Pattern 4: GoTo Cleanup → try/finally

Sub DoWork()
    Dim conn As Object
    Set conn = CreateObject("...")
    On Error GoTo Cleanup

    ' ... work with conn ...

Cleanup:
    conn.Close
    Set conn = Nothing
End Sub

def do_work():
    conn = create_connection()
    try:
        # ... work with conn ...
        pass
    finally:
        conn.close()

finally guarantees the cleanup code runs whether an exception occurred or not — exactly the same guarantee as VBA's GoTo Cleanup pattern.

VBA Labels → Comments

Labels that are only used as GoTo targets (not for error handling) are converted to comments by the converter, since Python has no label concept.

StartProcess:
    ' code here
Done:
    Exit Sub

# label: StartProcess
    # code here
# label: Done
    return

Related Guides

• Complete Syntax Mapping Reference — All operators, control flow, and error handling patterns.
• Complete Migration Guide — End-to-end process for migrating a VBA project.
• VBA Loops to Python — GoTo retry patterns are really loops in disguise.