Mock pip-compile to Resolve Requirements in Python

A mock function that mimics pip-compile by converting a requirements.in file into pinned, locked package versions.

Easy Python 3.9+ Aug 9, 2026 Modern tooling 12 views 0 copies

pip-tools requirements mock dependency-management

Python code

35 lines

Python 3.9+

import subprocess
import tempfile
from pathlib import Path


def compile_requirements_mock(requirements_in: str) -> str:
    """Mock pip-compile: resolve a simple requirements.in into a locked format."""
    lines = [line.strip() for line in requirements_in.splitlines() if line.strip() and not line.startswith("#")]
    result = []

    # Simulate resolving packages to pinned versions
    mock_versions = {
        "django": "4.2.7",
        "requests": "2.31.0",
        "flask": "3.0.0",
    }

    for line in lines:
        package = line.split("=")[0].split(">")[0].split("<")[0].strip()
        version = mock_versions.get(package, "1.0.0")
        result.append(f"{package}=={version}")

    return "\n".join(result)


if __name__ == "__main__":
    sample_input = """\
# Core dependencies
django>=4.0
requests==2.31.0
flask<4
"""
    locked = compile_requirements_mock(sample_input)
    print("Compiled requirements:")
    print(locked)

Output

stdout

Compiled requirements:
django==4.2.7
requests==2.31.0
flask==3.0.0

How it works

This function simulates the pip-tools pip-compile workflow by parsing a requirements.in string, stripping comments and blank lines, then mapping each package to a mock pinned version. It uses string splitting to extract package names from constraints like >=, ==, and <. The mock version dictionary hard-codes realistic versions for popular packages. Running as a script demonstrates the output format of a compiled/locked requirements file, typical of real pip-compile output.

Common mistakes

Not stripping whitespace before splitting versions, causing parsing errors
Assuming every line has a version constraint, breaking on plain package names
Forgetting to ignore comments and blank lines when parsing the input

Variations

Parse the input with `regex` or `packaging.requirements` for robust handling
Fetch real latest versions from PyPI using `requests` instead of a hard-coded dict

Real-world use cases

Testing CI pipelines without installing pip-tools by mocking the compile step
Generating example lock files for documentation or tutorials
Prototyping dependency resolution logic before integrating real pip-compile

Mock pip-compile to Resolve Requirements in Python

Python code

Output

How it works

Common mistakes

Variations

Real-world use cases

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