If a package has been discovered to be malicious, it will be taken down. The npm advisories link for malicious npm packages is mostly a history if you're looking at packages to download. There isn't a need for a service to tell you whether a package you're about to download is malicious (because it would not exist).
On the other hand, when looking at currently installed packages, in npm, there's a built in feature,
npm audit, which will tell you if the packages you're using have vulnerabilities (including known malicious packages). This is actually a newish feature, only released in the past year.
It appears this isn't built in to PIP, but there's a well known package called
safety: https://pypi.org/project/safety/ that achieves the same functionality. It looks like this achieves your goals?