Python bot "Killed" (exit code 137)

What 137 means

Exit code 137 is 128 plus 9, and 9 is SIGKILL: the process was ended from outside. On a server with a memory limit, that is almost always the limit being reached. Because the process is stopped rather than failing, there is no Python exception to catch.

In a discord.py bot

discord.py caches the last 1,000 messages by default, and with the members intent it downloads and keeps every member of every server at startup. On a bot in a few large servers, that is most of the memory. Turn off what you do not use.

import discord

client = discord.Client(
    intents=discord.Intents.default(),
    max_messages=100,  # or None to keep no message cache
    member_cache_flags=discord.MemberCacheFlags.none(),
    chunk_guilds_at_startup=False,
)

Everywhere else

Reading a whole file or API response into memory, a list that is appended to and never cleared, and heavy libraries imported for one function (pandas is the usual example) are the other common causes. Python's tracemalloc module shows which lines allocate the most; log its top entries every few minutes and look for the one that keeps growing.

A small Python bot fits comfortably in the 256 MB our free servers have. If yours has genuinely outgrown it, the paid plan gives it more room on the same server.