A Space Before the `=` in My .env File Made a Credential Silently Disappear

I have four different load_env() functions in my MCP server project ( my-git-manager ) — one in server.py , one in publish_devto.py , one in reply_comments.py , one in scripts/list_all_published_titles.py . All four exist for the same dumb reason: this repo has no dependency on python-dotenv , so each script that needs GITHUB_TOKEN or DEV_TO_API reads .env by hand. I went digging for a fresh bug in this repo this week — I write a lot about it, and the well is getting shallow — and decided to actually diff all four load_env() implementations against each other instead of reading them one at a time like I usually do. They'd never been compared side by side before. That's how I found this one. The line that started it Every one of them does roughly this: for line in f : line = line . strip () if " = " in line and not line . startswith ( " # " ): k , v = line . split ( " = " , 1 ) os . environ . setdefault ( k , v . strip (). strip ( '"' ). strip ( "'" )) Look closely at what gets .strip() ed there. v — the value — gets stripped of whitespace and surrounding quotes. k — the key, the actual name of the environment variable — gets nothing. That's fine if your .env file looks like this: DEV_TO_API = abc123 It's not fine if it looks like this: DEV_TO_API = abc123 Spaces around = are a completely normal thing to type. Plenty of .env examples online use them. Plenty of people reach for that style out of habit from other config formats. And line.split("=", 1) doesn't care — it splits on the first = no matter what's next to it, so k comes out as "DEV_TO_API " , trailing space included. What that trailing space actually does os.environ.setdefault("DEV_TO_API ", "abc123") sets an environment variable. It's just not the one anything is looking for. Every caller in this repo does os.environ.get("DEV_TO_API") — no trailing space, because that's the name everyone actually types. That lookup returns None , or whatever was already sitting in the environment before .env ever got read. I