The problem is that, instead of getting a MemoryError, Python tries to "go out of bounds" and allocate more memory than the cgroup allows, causing Linux to kill the process.

A workaround is to set RLIMIT_AS to the contents of /sys/fs/cgroup/memory/memory.limit_in_bytes, which is more or less what Java does when that flag is enabled (there are more things: cgroups v2 has a different path I think).

Setting RLIMIT_AS, we get the MemoryError as expected, instead of a SIGKILL.

My proposal is to either make it the default or hide it behind some sort of flag/environment variable, so users don't need to do that everywhere...

PS: On java, that flag also causes its OS API to return the limits when asked for how much memory is available, instead of returning the host's memory (default behavior).

PS: I'm not an avid Python user, just an ops guy, so I mostly write yaml these days... please let me know if I said doesn't make sense. 

Thanks!