Build the first working project virtualenv

Build only what the claim requires: activated venv imports pandas at a recorded version while a second project stays untouched. Prefer boring, deterministic code over frameworks you cannot yet explain. Run the path twice; identical output on this fixture is a feature, not a lack of creativity.

source .venv/bin/activate
python -m pip install -r requirements.txt
python -c "import pandas as pd; print(pd.__version__)"

Expected evidence: 2.2.2 (or pinned version). Read each printed intermediate as part of the argument that the path works—not as decoration.

Narrate the journey from raw input to result for a single example from project dir lab-env/ with requirements.txt containing pandas==2.2.2. If you cannot name an intermediate, the implementation is still too opaque for this lab. Only after this path is solid should you generalize data sources or UI.

While implementing the project virtualenv, print or log at least three intermediates that map to the claim (activated venv imports pandas at a recorded version while a second project stays untouched). Good intermediates are values a teammate could recompute with a calculator or diff. Bad intermediates are framework traces you cannot explain.

Re-run with project dir lab-env/ with requirements.txt containing pandas==2.2.2 twice. If the second run differs, either the path is nondeterministic (document the seed) or you have hidden global state—both are lab bugs until named.

Stop adding features once the path supports install project packages without mutating the global interpreter. Extra UI, extra tools, or extra models belong in later chapters. The mastery bar for this page is simply: a deterministic end-to-end path with intermediates.

At the implementation stage for python-virtual-environments, the job is narrower than finishing a product demo. You are creating one progressive evidence piece about project dir lab-env/ with requirements.txt containing pandas==2.2.2 that later pages inherit without redefining success. Keep that fixture small enough to inspect by hand, keep outputs copy-pasteable as text, and refuse to narrate this baseline as if it were a production SLA: record global site-packages pandas version (or absence) before creating the venv.

For this page specifically, success looks like a deterministic path with printed intermediates while still centering the user decision to install project packages without mutating the global interpreter. If you cannot point to a file, command, or assertion that proves that for the project virtualenv, stay on this page instead of advancing.

Set up a virtual environment

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