The current carat match algorithm matches pre-release versions (-alpha, -beta). NPM only considers those versions which are not pre-releases. Given that the carat match was added explicitly to mirror the NPM extension, it seems like identical behavior is desired.

For example, search for the "babel" package from semver and then use "^5.0.0" as the search term. None of the 5.0.0-betas are selected. Using python-semanticversion, they would match.

To fix this will require adjusting existing tests -- and therefore potentially breaking existing behavior.