Diagnostics

ty provides diagnostics that include snippets of your source code, annotations and helpful explanations. It will sometimes also provide suggestions on how to fix the reported issues.

Example: Typed dictionaries

In this first example, ty detected an invalid assignment to a TypedDict key. Notice how the diagnostic includes both the context around the line with the error, as well as the reference to the age item in the TypedDict definition:

When a TypedDict key is misspelled, ty will suggest the correct spelling. If you are using an editor with language server support, you can also apply this suggestion as a quick fix:

Example: Invalid arguments

Here, a file has been opened for writing in text mode, but we are trying to write bytes to it. The diagnostic points out the type mismatch and also includes the corresponding parameter in the function definition for write:

Example: Backwards compatibility

Instead of just telling you that tomllib can not be found, ty will tell you why it is not available for your project. In this case, your project is targeting Python 3.10, but tomllib was only added in Python 3.11: