uv --no-compile-bytecode seems to have no effect in Docker build

[akx]

Given a minimal Dockerfile

FROM ghcr.io/astral-sh/uv:0.4.16-python3.12-bookworm-slim
RUN find / -name '*.pyc' | wc -l
RUN uv pip install --system --no-compile-bytecode --no-cache-dir hai
RUN find / -name '*.pyc' | wc -l

and building it:

$ env BUILDKIT_PROGRESS=plain docker build .
#0 building with "default" instance using docker driver

#1 [internal] load build definition from Dockerfile
#1 transferring dockerfile: 269B done
#1 DONE 0.0s

#2 [internal] load metadata for ghcr.io/astral-sh/uv:0.4.16-python3.12-bookworm-slim
#2 DONE 0.9s

#3 [internal] load .dockerignore
#3 transferring context: 2B done
#3 DONE 0.0s

#4 [1/4] FROM ghcr.io/astral-sh/uv:0.4.16-python3.12-bookworm-slim@sha256:cdb69914e2b70a8c0c8a01af28780bfe6c1b5fad2167207b7da5f328b3f8cc0f
#4 resolve ghcr.io/astral-sh/uv:0.4.16-python3.12-bookworm-slim@sha256:cdb69914e2b70a8c0c8a01af28780bfe6c1b5fad2167207b7da5f328b3f8cc0f done
[...]
#4 DONE 1.7s

#5 [2/4] RUN find / -name '*.pyc' | wc -l
#5 0.111 0
#5 DONE 0.2s

#6 [3/4] RUN uv pip install --system --no-compile-bytecode --no-cache-dir hai
#6 0.273 Resolved 1 package in 87ms
#6 0.287 Prepared 1 package in 13ms
#6 0.288 Installed 1 package in 0.42ms
#6 0.288  + hai==0.3.0
#6 DONE 0.3s

#7 [4/4] RUN find / -name '*.pyc' | wc -l
#7 0.125 35
#7 DONE 0.1s

#8 exporting to image
#8 exporting layers 0.0s done
#8 writing image sha256:4685627209911f9fe7de6f8993524824553cc4e59c15cd1097f56cc38736a360 done
#8 DONE 0.0s

See steps 5 and 8 – there were zero pyc files in the container to begin with, after uv pip install --system --no-compile-bytecode there were 35.

• --no-compile-bytecode isn't actually documented either, but compile-bytecode is documented to be false by default, so I shouldn't be getting .pycs anyhow?
• Setting PYTHONDONTWRITEBYTECODE=1 doesn't have an effect (not that I expected it to).

[konstin]

These files are created earlier then installation and bytecode compilation, they are created during interpreter discovery: uv runs a small script to collect information on the Python interpreter, such which wheel tags it supports. This script runs with -I (#2552), so it ignores PYTHONDONTWRITEBYTECODE and other PYTHON* options. This way Python bytecode compiles the parts of std that are used by the script.

[akx]

Huh. That seems to imply that there is, at present, no way to actually have no .pyc files get created? 😕

EDIT: #7707 :)