Python Interview Questions
Virtual environments, dependency management, pyproject.toml/wheels, and Python's environment/CLI/filesystem standard library.
Ans
Environment variables provide configuration outside source code and can be read with os.environ or os.getenv.
Example
pythonimport os port = int(os.getenv("PORT", "8000")) print(port)
Important Point
Do not store secrets directly in source code; use appropriate secret/configuration management.
Ans
pathlib provides object-oriented path handling that is generally clearer and more portable than manually concatenating path strings.
Example
pythonfrom pathlib import Path path = Path("data") / "input.txt" print(path)
Important Point
Use Path operations instead of hard-coded OS-specific separators.
Ans
argparse is a standard-library module for parsing command-line arguments and generating help messages.
Example
pythonimport argparse p = argparse.ArgumentParser() p.add_argument("--name", default="Guest") args = p.parse_args() print(args.name)
Important Point
Validate arguments and provide useful help/error messages for command-line tools.
Ans
venv is Python's standard-library mechanism for creating virtual environments. virtualenv is a separate, older and feature-rich third-party tool that can support additional workflows.
Example
bashpython -m venv .venv
Important Point
For many projects, built-in venv is sufficient; follow the team's tooling choice.
Ans
Dependency management records, resolves, and installs the external packages a project needs, ideally with reproducible versions and environments.
Example
textpyproject.toml requirements.txt lock file/tooling
Important Point
Modern Python projects often use pyproject.toml plus a package/dependency manager rather than relying only on requirements.txt.
Ans
pyproject.toml is a standardized configuration file used by Python projects for build systems, project metadata, dependencies, and tool configuration.
Example
toml[project] name = "sample-app" version = "0.1.0"
Important Point
The exact fields and supported tools depend on the chosen packaging/build configuration.
Ans
Packaging turns Python project code into a distributable structure or artifact that can be installed and reused. Modern projects commonly define metadata and build settings in pyproject.toml.
Example
textsrc/ package_name/ pyproject.toml
Important Point
Keep package metadata, dependencies, and build configuration consistent with the selected build backend.
Ans
A wheel is a built Python distribution format designed for installation without running a source build in many cases.
Example
textpackage_name-1.0.0-py3-none-any.whl
Important Point
A wheel's compatibility tags indicate which Python/platform combinations it supports.
Ans
A source distribution, commonly an sdist, contains source files and packaging metadata from which a package can be built.
Example
textpackage_name-1.0.0.tar.gz
Important Point
Installing an sdist can require build tools or compilation for packages with native extensions.
Ans
Activation changes shell commands such as python and pip to use the virtual environment's interpreter by adjusting environment variables such as PATH.
Example
bash# Unix-like shells source .venv/bin/activate
Important Point
Activation is a convenience; you can also invoke the environment's interpreter directly.
Ans
A dependency conflict occurs when installed packages require incompatible versions of the same dependency.
Example
textPackage A -> library >=2 Package B -> library <2
Important Point
Use isolated environments and a resolver/lock strategy to make dependency versions reproducible.
Ans
Dependency injection means passing dependencies into a component instead of creating them internally, making code easier to test and replace.
Example
pythonclass OrderService: def __init__(self, payment_gateway): self.payment_gateway = payment_gateway service = OrderService(FakePaymentGateway())
Important Point
Python's flexible objects make simple constructor injection sufficient for many projects; a DI framework is not always necessary.
Ans
Path.exists() checks whether a filesystem path exists.
Example
pythonfrom pathlib import Path p = Path("data.txt") print(p.exists())
Important Point
Existence checks can race with later operations; for critical file operations, handle the actual operation's exception as well.
Ans
os.environ exposes the process environment variables as a mapping-like object.
Example
pythonimport os mode = os.environ.get("APP_MODE", "dev") print(mode)
Important Point
Environment variables are strings; convert them to the required type.
Ans
subprocess lets Python start and communicate with external processes.
Example
pythonimport subprocess result = subprocess.run(["python", "--version"], capture_output=True, text=True) print(result.stdout or result.stderr)
Important Point
Prefer argument lists over shell command strings and be careful with `shell=True` when inputs are untrusted.
Ans
sys.argv contains command-line arguments passed to a Python script, with the script name normally at index zero.
Example
pythonimport sys print(sys.argv)
Important Point
For nontrivial command-line interfaces, argparse provides parsing, validation, and help output.
Ans
sys.path is the list of locations Python searches for modules during imports.
Example
pythonimport sys print(sys.path)
Important Point
Changing sys.path at runtime can hide packaging problems; prefer proper packages and environment configuration.