I’ve run into this exact headache with SolidWorks’ COM API in Python before—those ref parameters are tricky because Python’s native integers don’t play nice with COM’s mutable reference types. Let’s break down how to fix this, including a critical mistake in your original code that’s compounding the issue.

The Root Cause #

Your Type mismatch error comes from two issues:

1. COM’s ref int expects a mutable integer reference that the function can modify in-place. Python’s standard int is immutable, so passing it directly means the COM runtime can’t write back to it, triggering the type error.
2. You’re misordering parameters in your OpenDoc6 call! The function signature has a string Configuration as the 4th parameter, but you’re passing your error integer there instead—this alone would cause a type mismatch between a string and integer.

The Solution #

First, fix the parameter order. Then, wrap your ref parameters in a VARIANT object that explicitly marks them as by-reference integers. This tells win32com to handle them correctly with the COM runtime.

Step 1: Add Required Imports

You’ll need to import the VARIANT type and associated constants from win32com.client:

import win32com.client
from win32com.client import VARIANT, VT_I4, VT_BYREF

Step 2: Wrap ref Parameters

Replace your error and warning variable initialization with VARIANT objects. These act as mutable containers that COM can modify:

# Initialize ref parameters with VARIANT (by-reference 32-bit integer type)
error = VARIANT(VT_BYREF | VT_I4, int(swConst.swFileNotFoundError))
warning = VARIANT(VT_BYREF | VT_I4, int(swConst.swFileLoadWarning_AlreadyOpen))

Step 3: Call OpenDoc6 Correctly

Make sure the parameter order matches the function signature: FileName, Type, Options, Configuration, Errors, Warnings. Pass an empty string for Configuration if you don’t need a specific config:

swModel = swApp.OpenDoc6(fileName, docType, config, "", error, warning)

Step 4: Access Updated Values

After the call, you can get the actual error/warning codes returned by SolidWorks using the .value attribute of the VARIANT objects:

print(f"Final error code: {error.value}")
print(f"Final warning code: {warning.value}")

Full Modified Code #

import sldworksPython as solidWorks
import sldconstPython as solidConst
import win32com.client
from win32com.client import VARIANT, VT_I4, VT_BYREF

swApp: solidWorks.ISldWorks = win32com.client.Dispatch(solidWorks.SldWorks.CLSID)
swConst = solidConst.constants

fileName = "Assem Of Hinge.SLDASM"
docType = int(swConst.swDocASSEMBLY)
config = int(swConst.swOpenDocOptions_AutoMissingConfig)

# Initialize ref parameters with mutable VARIANT containers
error = VARIANT(VT_BYREF | VT_I4, int(swConst.swFileNotFoundError))
warning = VARIANT(VT_BYREF | VT_I4, int(swConst.swFileLoadWarning_AlreadyOpen))

# Call OpenDoc6 with correct parameter order
swModel = swApp.OpenDoc6(fileName, docType, config, "", error, warning)

# Verify results
if swModel is not None:
    print("Document opened successfully!")
else:
    print(f"Failed to open document. Error code: {error.value}, Warning code: {warning.value}")

内容的提问来源于stack exchange，提问作者Mr.Sha1