Find the interpreterThe python command can point to different executables. which python and python -V agree with the project.
Programming setup
Python Virtual Environments for Makers
Learn why Python projects use virtual environments and how to prove which interpreter and packages are active.
Ladder steps
Each step should prove one idea before the project asks for the next one.
Create an environmentA virtual environment isolates packages from the system Python. The venv directory contains its own bin/python.
Activate deliberatelyActivation changes PATH for the current shell. which python points inside the venv.
Freeze only when usefulrequirements files record dependencies for another environment. pip freeze should match the project, not global clutter.
Examples to inspect
Use examples to read signals, not as blind recipes.
Check active Python
python -V && which pythonExpected signal: Version and executable path
Create a local virtual environment
python -m venv .venvExpected signal: A .venv folder with bin/python
Activate and list packages
. .venv/bin/activate && python -m pip listExpected signal: Packages installed in that environment
Common traps
- Installing with one pip and running another python.
- Committing a whole virtual environment.
- Using sudo pip for a project dependency.
Practice task
Create a tiny venv, install one package, and prove which python and pip are active.
Next steps
- Learn Git ignores.
- Learn deployment paths.
- Learn package lock errors.
Practice ladder
- Near-Copy Rebuild: Recreate one example, decision path, or worked explanation from Python Virtual Environments for Makers. Keep most givens the same, then implement, test, and explain while naming each cue you used. Use the lesson's example block when it helps.
- One-Change Transfer: Change exactly one condition, number, input, symptom, material, or constraint from the near-copy case. Then implement, test, and explain again and explain what changed.
- Mixed Review Set: Interleave this topic with one prerequisite or adjacent idea. Write three short prompts: one recall, one application, and one comparison.
- Find And Fix The Error: Invent a plausible wrong answer, unsafe step, invalid assumption, or bad classification. Mark the first point where it goes wrong, then correct it using the lesson's check.
Flashcard preview
What does a virtual environment isolate?
It gives a project its own interpreter path and package set.
What does the 'Find the interpreter' step prove?
The python command can point to different executables. Check: which python and python -V agree with the project.
What does the 'Create an environment' step prove?
A virtual environment isolates packages from the system Python. Check: The venv directory contains its own bin/python.
What does the 'Activate deliberately' step prove?
Activation changes PATH for the current shell. Check: which python points inside the venv.
What does the 'Freeze only when useful' step prove?
requirements files record dependencies for another environment. Check: pip freeze should match the project, not global clutter.
When would you use `python -V && which python`?
Use it to check active python. Expected signal: Version and executable path
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Related paths
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Study assets
Project context
- Deploy a Static Site on a VPS
- Browse Programming Workflow
- Next ladder clue: Learn Git ignores.
Related references
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