I am pleased to announce the release of xlwings v0.4.0: The most important update with this release was made on Windows: The methodology used to make a connection to Workbooks has been completely replaced. This finally allows xlwings to reliably connect to multiple instances of Excel even if the Workbooks are opened from untrusted locations (network drives or files downloaded from the internet). This gets rid of the dreaded "Filename is already open..." error message that was sometimes shown in this context. It also allows the VBA hooks ("RunPython") to work correctly if the very same file is opened in various instances of Excel. Check the Release Notes for full details: http://docs.xlwings.org/whatsnew.html About xlwings: xlwings is a BSD-licensed python library that makes it easy to call python from Excel and vice versa: Interact with Excel from python using a syntax that is close to VBA yet pythonic. Replace your VBA macros with python code and still pass around your workbooks as easily as before. xlwings fully supports NumPy arrays and Pandas DataFrames. It works with Microsoft Excel on Windows and Mac. http://xlwings.org