PyFlowLens

Understand Python code without reading every line.

PyFlowLens statically analyzes your Python (FastAPI) project and visualizes the entire execution flow — function calls, data transformations, branch logic, and dependency injection chains — in an interactive graph inside VS Code.

What It Does

• See how your API works — one click shows the full execution path from HTTP request to response
• See what breaks when you change code — impact analysis traces your changes through the call graph
• See which code actually ran — send a real request and watch the execution path light up

Views

Review Brief

Get a quick summary: risk scores, key concerns, decision points, and error paths — before you dive into the code.

Code Flow

Execution steps with actual source code inline. See what the code does in the order it runs.

Data Flow

Follow the data: query → transform → validate → branch → respond. See how variables flow through your API.

Call Stack

Classic function call graph. Drill down from the API trigger (L0) through services (L1-L2) to individual statements (L4).

CFG (Control Flow Graph)

Branches, loops, and exception paths visualized with source code. Human-readable branch labels like "user exists" / "user is None" instead of generic yes/no.

Change Impact Analysis

Changed a function? Click "Analyze Uncommitted Changes" in the sidebar to instantly see:

• Which functions you modified
• Which API endpoints are affected (including through Depends() chains)
• Risk score and call depth for each endpoint

Runtime Tracing

Send an actual HTTP request from the sidebar and see which code paths were executed:

• HIT (green) — this code ran
• MISS (dimmed) — this code was skipped
• RUNTIME-ONLY — only seen at runtime, not in static analysis

Quick Start

1. Install the extension
2. Open a Python (FastAPI) project
3. Run PyFlowLens: Analyze Project from the command palette (Ctrl+Shift+P)
4. Click any endpoint in the sidebar to visualize its flow

Commands

Requirements

• Python 3.9+
• A FastAPI project (other frameworks coming soon)

Feedback & Issues

Found a bug? Have a feature request?

• GitHub Issues
• Source Code

Contributions and feedback are always welcome!