Turns out it was introduced in 3.8, released in 2019, so it was much too late to inspire Go

You are probably right about that. But don't forget that the operator didn't made it day one, there was lot of discussion before and probably testing it in the beta releases before. But given how old Golang at that point is, you are right about my take on inspiration. This operator wasn't a new invention in Python.

It also has a substantially different meaning than in Go.

I don’t know if there’s an “official” rationale for the Go syntax, but := is a fairly common (but not ubiquitous) math notation meaning “define the thing on the left to be equal to the expression on the right”, i.e. to distinguish it from the other use of =, i.e. “the expression on the left must be equal to the expression on the right.”

~~Does it though? In both cases, Go and Python, the operator will assign a variable a value and also use it as an expression. That is useful in cases like for loops or other cases where you want immediately use the variable content as an expression. This cannot be done with the regular assignment operator a = 69, which itself is not an expression. So in practical terms, its the same in usability for Go and Python. So its doing the same for both languages and has the same differences to the assignment operator.~~ (Edit: Read the reply, I learned something myself. That's why its important that you don't blindly teach people like I did.)