Python 3.9 has been released fairly recently and it was a bit too short notice for us to ensure it works with IDA 7.5 Service Pack 3 (if you have tried it, you may have had a bad time.)
We have now added support for Python 3.9 in IDAPython. Here’s how you can get it to work (only if you need Python 3.9; IDA already works fine with 3.8 or earlier versions):
- Make sure you are using IDA 7.5 SP3
- Download the appropriate package for your platform below
- Unpack the package in the directory of your IDA installation
- Run the
idapyswitchbinary (on Windows, from admin command prompt)
Everything should then work as intended.