Python 2.7¶

This section introduces the Python 2.7 packaging workflow built around pip, setup.py, and requirements.txt, using a small command-line project to show how pinned dependency files improved reproducibility.

Applied Project¶

Project Setup¶

The applied project is Historic Calculator, release 4.0.0. This snapshot is set in 2010, the release year of Python 2.7, and contains the historic_calculator package plus the hist_calc command-line script.

Run the Project¶

Application commands are documented in the section README.

Background¶

This project belongs to the Python 2.7 era that began in 2010, when pip and requirements.txt became the practical packaging workflow for many teams. The common layout paired setup.py with a pinned requirements file for:

Declaring abstract package metadata and entry points
Recording install-time runtime dependencies
Pinning a concrete dependency set for repeatable installs
Building source distributions for release

setup.pyrequirements.txt

The setup.py file keeps the package metadata, abstract runtime dependency, and console-script registration:

setup(
    name="historic_calculator",
    version="4.0.0",
    description="A tiny vector calculator using NumPy and setuptools.",
    package_dir={"": "src"},
    packages=["historic_calculator"],
    install_requires=[
        "numpy",
    ],
    entry_points={
        "console_scripts": [
            "hist_calc = historic_calculator.main:main_cli",
        ],
    },
)

name gives the distribution its package name.
version records the release number that build and install commands use.
description adds a short human-readable project summary to the package metadata.
package_dir maps packages to the src directory instead of the project root.
packages lists the Python package included in the distribution.
install_requires records the abstract NumPy runtime dependency.
entry_points registers the hist_calc command through console_scripts.

The concrete deployment pin lives in requirements.txt:

numpy==1.9.2

numpy==1.9.2 pins the exact NumPy release used by this project snapshot.

Dependency Management¶

Overview¶

pip and requirements.txt made dependency installation more practical, but the model still had important limits:

⚠️ requirements.txt was a pinned install input, not a complete lockfile with hashes.
⚠️ Environment isolation was still a separate concern and was not provided by pip itself.
⚠️ Older pip behavior lacked the modern resolver used by current Python workflows.

Runtime and build dependencies¶

Use Dockerfile.devEnv for the Python 2.7 development environment. It keeps the historical interpreter, pip-era tooling, and build tooling isolated from the host machine.

NumPy replaces the earlier Numeric packages as the runtime component for array-style calculations. requirements.txt pins the exact NumPy version, so pip install -r requirements.txt can reproduce the dependency set more reliably than the manual download steps used in earlier sections.

Install the pinned runtime dependencies:

pip install -r requirements.txt

This installs the concrete dependency set for the Python 2.7 workflow before the project package is installed.

Build the package¶

Build the source distribution:

python setup.py sdist

The era predates PEP 427 wheels, so the source distribution is the canonical artifact.

Install the package¶

Install the project itself:

python setup.py install