Python 3.6 vs 3.5 TypeError message on string concatenation

Question

'Hello ' + 1 doesn't return the same error message on Python 3.5 and 3.6:

• Python 3.5.2: TypeError: Can't convert 'int' object to str implicitly
• Python 3.6.0: TypeError: must be str, not int

Is it a simple change in wording or is there something more subtle behind?

Answer 1

It was just some cleaning up of code that involved string objects. It also introduced some changes in the error messages when incompatible objects are used to make them a bit "more informative".

See: Issue 26057 - Avoid nonneeded use of PyUnicode_FromObject() that introduced this change if you're interested.

There's nothing subtle here, it is still illegal and all, the author changed the error message to what he considered a bit clearer.

Edit: I created Issue 29116 - Make str and bytes error messages on concatenation conform with other sequences to address this specific message while also addressing the error message for bytes types that have had a similarly verbose response when we do silly things with them:

>>> b'' + ''
TypeError: can't concat bytes to str