Wednesday 20 October 2010

StreamHandler’s newline terminator now configurable

When StreamHandler writes a formatted log message to its stream, it adds a newline terminator. This behaviour is inherited by FileHandler and the other classes which derive from it (such as the rotating file handlers).

For most people, that’s what they want, since they get log messages on separate lines without having to explicitly code newlines in their log messages. However, some people want the flexibility to not have this newline automatically appended to logged messages.

Starting with Python 3.2, the message terminator will be configurable. This has been done by adding a terminator attribute to StreamHandler, which when emitting an event now writes the formatted message to its stream first, and then writes the terminator. If you don’t want newline termination for a handler, just set the handler instance’s terminator attribute to the empty string.

There’s a small chance that this approach will cause unexpected behaviour – in the unlikely instance that someone is setting a terminator attribute on an a StreamHandler or one of its subclasses for their own, unrelated purposes. Other than that, the new behaviour should be backwards compatible.

If this change is likely to adversely affect you for any reason, please let me know, by replying to this post. The change has already been checked into the py3k branch, and you are welcome to try it out.

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