If you are a beginner you can learn Python inside Anvil. Your pace will be slow, the auto-completion is very likely to be sufficient and helpful, and Pycharm would be more overwhelming that helpful.
If you are an expert with Visual Studio and .NET I would get familiar with Python using Pycharm. There is auto-completion, documentation, linter, suggestions and all the goodies you may want.
The problem is that all the import anvil.* on a form will not work with Pycharm because they are only available on the Skulpt library loaded in the browser.