impscope 0.2.0

Python Dependency Impact Analyzer

impscope — Python Dependency Impact Analyzer

A small, fast tool to analyze Python file dependencies and assess the impact of changes. Pure standard library, no external deps.

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Features

• Impact analysis for a given file (direct & indirect dependents)
• Not-imported files report (files not imported by any other file)
• Dependency graph (most/least depended files, with sorting)
• Codebase statistics (totals)
• Exclude by glob patterns (e.g., --exclude "tests/*")
• Impact since a Git commit (since <commit>) — union blast radius of changed files
• Text and JSON output formats
• Source roots support (--source-root, --include-outside-roots)
• Strict/heuristic import resolution (--strict-resolution)
• Fast & lightweight (pure Python, AST-based)
• Python 3.7+

Installation

pip install impscope

Or install from source:

git clone https://github.com/zh-he/impscope.git
cd impscope
pip install -e .

Quick Start

# See what your current Python edits may affect
impscope

# Check the impact of changing a specific file
impscope impact models.py

# Show dependency statistics (brief overview)
impscope stats

# List files that are not imported by any other file
impscope unimported

# Show dependency graph (descending by default)
impscope graph

# Show least depended files
impscope graph --sort asc

# Analyze a specific directory and exclude tests/migrations
impscope --path src/ --exclude "tests/*" --exclude "*/migrations/*" stats

# Impact of files changed since last commit (Git required)
impscope since HEAD

# JSON output (great for CI)
impscope --format json since main

Tip: you can also run it as a module:

python -m impscope --help

Usage

impscope [GLOBAL_OPTIONS] <command> [COMMAND_OPTIONS]

Commands:
  impact FILE           Analyze the impact of changing a specific file
  unimported            List files that are not imported by any other file
  graph                 Show dependency graph (top most/least depended files)
  stats                 Show comprehensive dependency statistics
  since COMMIT          Analyze union impact of Python files changed since COMMIT
                        (e.g., HEAD~1, <hash>, <branch>)

Global options (must appear before the subcommand):
  --path PATH                 Root path to analyze (default: current directory)
  --exclude GLOB              Glob pattern to exclude (repeatable)
                              e.g., --exclude "tests/*" --exclude "*/migrations/*"
  --format {text,json}        Output format (default: text)
  --full                      Do not truncate long lists in text output
  --limit N                   Max items per list in text output when not using --full (default: 10)
  --source-root DIR           Treat DIR (relative to --path) as an import root (repeatable)
  --include-outside-roots     When --source-root is provided, also include files outside those roots
  --strict-resolution         Only resolve imports that exactly match indexed modules
                              (no parent-package fallback)
  --version                   Show version information
  --help                      Show help message

How It Works

impscope uses Python’s AST to:

1. Parse all Python files in your project
2. Extract import and from ... import ... statements (including relative imports)
3. Map files to modules (packages via __init__.py)
4. Build a dependency graph
5. Compute direct & indirect dependents (impact) via BFS

It handles:

• Regular imports (import module)
• From imports (from module import name)
• Relative imports (from .module import name, from .. import x)
• Packages and __init__.py
• Circular dependencies (no infinite recursion)
• Ignored directories: .git, .venv, __pycache__, node_modules, dist, build, etc.

Excludes

• --exclude patterns are matched against relative paths (POSIX style), e.g. src/app/models.py.
• You can repeat --exclude multiple times:

  impscope --exclude "tests/*" --exclude "*/migrations/*" stats
  

Source roots

• Use --source-root to treat one or more directories as import roots (relative to --path):

  impscope --path . --source-root src --source-root python stats
  

• With --include-outside-roots, files outside these roots are also scanned (module names computed relative to the project root).

Since

• Requires Git to be available, and the path to be inside a Git repo.
• Uses git diff --name-only --diff-filter=ACMR <commit>..HEAD to collect changed .py files, then computes the union of direct/indirect dependents across those files.
• When --path points to a subdirectory, only changes within that directory tree are considered for display and impact.
• --exclude patterns also apply to the changed file list for consistent reporting.

Import resolution notes (re: from u import x without dot)

• In Python 3, absolute imports are the default. Writing from u import x is treated as importing top-level module u on sys.path, not pkg.u.
• impscope follows this rule:
  • It resolves from u import x only if there is a module/package named u inside the analyzed root (--path).
  • If u actually lives under a package like pkg/u.py and there is no top-level u, impscope will not infer pkg.u from from u import x.
• Heuristic fallback (non-strict mode):
  • For import pkg.sub.mod it can fall back to the nearest existing parent (pkg.sub, then pkg).
  • For from pkg import *, it may map to pkg (or its nearest existing parent).
• Recommendations:
  • Within a package, prefer explicit relative imports: from .u import x.
  • Or use fully qualified absolute imports from your package root: from pkg.u import x.
  • Run impscope from the repository/package root so absolute imports can be mapped.

Note: The “least depended files” view in graph --sort asc ranks files that have at least one dependent. Files with zero dependents are listed by the unimported command.

Requirements

• Python 3.7+
• No external dependencies (standard library only)

Testing

python -m unittest discover -v

Contributing

Contributions are welcome! Please open an issue or pull request.

License

MIT License