ASPPY.ExecutePython

Run real CPython code directly from your Classic ASP / VBScript pages and get a string result back. This bridges the gap between your legacy VBScript web application and the full Python ecosystem — psutil, numpy, pandas, requests, Pillow, or any other package installed in your Python environment.

How It Works

Each call to ASPPY.ExecutePython spawns an isolated subprocess running the same Python interpreter that hosts ASPPY. Your VBScript code sends a Python source string to execute, and the Python snippet uses ASPPY_RETURN(value) to send a string result back to VBScript.

The flow is:

1. VBScript calls ASPPY.ExecutePython(pyCode).
2. ASPPY wraps the code with a runtime prelude that defines ASPPY_RETURN.
3. A fresh python subprocess runs the combined script.
4. The first ASPPY_RETURN(value) writes the payload to stdout and halts execution.
5. ASPPY captures the payload and returns it as a VBScript string.

Methods

The ASPPY_RETURN Convention

Inside every Python snippet or file, use the built-in ASPPY_RETURN(value) function to return a string to VBScript:

• First call wins. The first ASPPY_RETURN sets the return value and stops the snippet.
• Never called? The return value is "" (empty string).
• Always a string. For structured data, return JSON and decode it with ASPPY.json.Decode().

import json

# Do some computation
data = {"status": "ok", "count": 42}

# Return the result as a JSON string
ASPPY_RETURN(json.dumps(data))

Environment Variables

Sample: Inline Python

Embed Python directly in your ASP page. Use VBScript string concatenation (& and & vbCrLf) to build multi-line Python source:

<%
Dim pyCode, result

pyCode = "import platform" & vbCrLf & _
         "ASPPY_RETURN(f'Python {platform.python_version()} on {platform.system()}')"

result = ASPPY.ExecutePython(pyCode)
Response.Write("System: " & result)
%>

Sample: ExecutePythonFile

Place your Python code in a .py file under the web root and call it by relative path:

# www/scripts/status.py
import psutil, json

cpu = psutil.cpu_percent(interval=1)
mem = psutil.virtual_memory()

ASPPY_RETURN(json.dumps({
    "cpu_percent": cpu,
    "memory_used_gb": round(mem.used / (1024**3), 1),
    "memory_total_gb": round(mem.total / (1024**3), 1)
}))

<%
Dim jsonStr, stats
jsonStr = ASPPY.ExecutePythonFile("scripts/status.py")
Set stats = ASPPY.json.Decode(jsonStr)

Response.Write "CPU: " & stats("cpu_percent") & "%<br>"
Response.Write "RAM: " & stats("memory_used_gb") & " / " & stats("memory_total_gb") & " GB"
%>

Sample: Full Page — Python Processes

A complete working example that lists all running Python processes, sorted by memory usage:

<%@ Language="VBScript" %>
<%
Dim pyCode, jsonResult, procs

pyCode = _
    "import json, psutil"                                              & vbCrLf & _
    "rows = []"                                                        & vbCrLf & _
    "for p in psutil.process_iter(['pid', 'name', 'username', 'memory_info']):" & vbCrLf & _
    "    try:"                                                         & vbCrLf & _
    "        name = (p.info.get('name') or '')"                        & vbCrLf & _
    "        if 'python' in name.lower():"                             & vbCrLf & _
    "            mem = p.info.get('memory_info')"                      & vbCrLf & _
    "            mb = round(mem.rss / (1024 * 1024), 1) if mem else 0" & vbCrLf & _
    "            rows.append({"                                        & vbCrLf & _
    "                'pid': p.info.get('pid'),"                        & vbCrLf & _
    "                'name': name,"                                    & vbCrLf & _
    "                'user': p.info.get('username') or '',"           & vbCrLf & _
    "                'mem_mb': mb"                                     & vbCrLf & _
    "            })"                                                   & vbCrLf & _
    "    except (psutil.NoSuchProcess, psutil.AccessDenied):"          & vbCrLf & _
    "        continue"                                                 & vbCrLf & _
    "rows.sort(key=lambda r: r['mem_mb'], reverse=True)"               & vbCrLf & _
    "ASPPY_RETURN(json.dumps(rows))"

On Error Resume Next
jsonResult = ASPPY.ExecutePython(pyCode)

If Err.Number <> 0 Then
    Response.Write "<p style='color:#b00'>Error: " & _
        Server.HTMLEncode(Err.Description) & "</p>"
    Err.Clear
    Response.End
End If
On Error Goto 0

procs = ASPPY.json.Decode(jsonResult)
%>
<table>
    <tr><th>PID</th><th>Name</th><th>User</th><th>Memory (MB)</th></tr>
<%
Dim i, proc
For i = 0 To UBound(procs)
    Set proc = procs(i)
    Response.Write "<tr><td>" & proc("pid") & "</td><td>" & _
        proc("name") & "</td><td>" & proc("user") & _
        "</td><td>" & proc("mem_mb") & "</td></tr>"
Next
%>
</table>

Error Handling

Wrap ASPPY.ExecutePython calls in On Error Resume Next to handle failures gracefully. Common errors include:

• Feature disabled — ASP_PY_ALLOW_PYTHON not set.
• Module not found — the Python package is not installed in the interpreter.
• Syntax error — the Python snippet has invalid syntax.
• Timeout — the snippet ran longer than ASP_PY_PYTHON_TIMEOUT.

<%
On Error Resume Next
Dim result
result = ASPPY.ExecutePython("ASPPY_RETURN('hello')")

If Err.Number <> 0 Then
    Response.Write "Python error: " & Server.HTMLEncode(Err.Description)
    Err.Clear
Else
    Response.Write "Result: " & result
End If
On Error Goto 0
%>

Setting Up Under NSSM

If you run ASPPY as a Windows service via NSSM, set the environment variable in the service configuration:

nssm set YourServiceName AppEnvironmentExtra ASP_PY_ALLOW_PYTHON=1
nssm restart YourServiceName

Why Use This?