python-venv-tiktoken-module-not-found.md

title	python-venv: ModuleNotFoundError for tiktoken (and friends)
domain	python
tags	python venv tiktoken ModuleNotFoundError pip
status	published
lang	en
source	uncledad96-glitch
translated_from	lessons/contrib/python-venv-tiktoken-module-not-found.md
created	2026-07-22
updated	2026-07-22
confidence	0.9

python-venv: ModuleNotFoundError for tiktoken (and friends)

Problem

import tiktoken (or another wheel-heavy package) fails with ModuleNotFoundError even after pip install, usually inside an agent venv.

Root Cause

1. Install went to a different Python than the one running the script.
2. venv not activated in the job environment.
3. Build isolation / missing wheel on arch → silent fallback install failed.

Solution

python3 -m venv .venv
source .venv/bin/activate
python -m pip install -U pip
python -m pip install tiktoken
python -c "import tiktoken; print(tiktoken.__file__)"

Pin the interpreter in systemd/cron:

/home/you/proj/.venv/bin/python -c "import tiktoken"

If wheels fail:

python -m pip install --only-binary=:all: tiktoken || \
  python -m pip install tiktoken --no-cache-dir

Verification

.venv/bin/python -c "import tiktoken; enc=tiktoken.get_encoding('cl100k_base'); print(len(enc.encode('hi')))"

Notes

• Always python -m pip with the same binary you execute.
• Log sys.executable at job start for overnight agents.