detective-snapshot 0.1.3

A package for capturing and comparing function input/output snapshots

Detective Snapshot 🕵️‍♂️🔍

A Python package for capturing function input/output snapshots. Perfect for debugging, testing, and understanding complex function call hierarchies.

Features

• 📸 Capture function inputs and outputs
• 🌳 Track nested function calls
• 🎯 Select specific fields to snapshot
• 📦 Support for Python objects, dataclasses, and protobufs

Install

pip install detective-snapshot

Quick Start

from detective import snapshot

@snapshot()
def calculate_cat_food(cats):
    total = sum(get_cat_appetite(cat) for cat in cats)
    return f"Need {total}oz of food per day"

@snapshot()
def get_cat_appetite(cat):
    # Cats eat about 0.5oz per pound of weight
    return cat["weight"] * 0.5

# Feed the kitties
cats = [
    {"name": "Whiskers", "weight": 10},
    {"name": "Chonk", "weight": 15}
]
result = calculate_cat_food(cats)

With debug mode on, each call to an outermost decorated function creates a new snapshot file in ./debug_snapshots/ with a unique UUID:

{
    "FUNCTION": "calculate_cat_food",
    "INPUTS": {
        "cats": [
            {"name": "Whiskers", "weight": 10},
            {"name": "Chonk", "weight": 15}
        ]
    },
    "OUTPUT": "Need 12.5oz of food per day",
    "CALLS": [
        {
            "FUNCTION": "get_cat_appetite",
            "INPUTS": {"cat": {"name": "Whiskers", "weight": 10}},
            "OUTPUT": 5.0
        },
        {
            "FUNCTION": "get_cat_appetite",
            "INPUTS": {"cat": {"name": "Chonk", "weight": 15}},
            "OUTPUT": 7.5
        }
    ]
}

Field Selection

Capture only the fields you care about:

@snapshot(
    input_fields=["cat.name", "cat.weight"],
    output_fields=["daily_food"]
)
def calculate_cat_diet(cat):
    daily_food = cat["weight"] * 0.5
    return {"daily_food": daily_food, "feeding_schedule": "twice daily"}

Selection Patterns

Pattern	Example	Description
Direct Field	name	Select a field directly from root
Nested Field	cat.weight	Navigate through nested objects
Array Index	cats[0].name	Select specific array element
Array Wildcard	cats[*].weight	Select field from all array elements
Multiple Fields	cat.(name,weight)	Select multiple fields from an object
Wildcard Object	pets.*.name	Select field from all child objects
Args Syntax	args[0].name	Select from function arguments
Mixed Access	pets[*].records.*.weight	Combine array and object access

Full JSONPath support is also available for more complex queries.

Advanced Usage

Capture Complex Objects

@dataclass
class Cat:
    name: str
    breed: str
    medical_records: List[Record]

@snapshot(input_fields=["cat.medical_records[*].weight"])
def track_weight_history(cat: Cat):
    return [record.weight for record in cat.medical_records]

Handle Nested Function Calls

@snapshot()
def process_cattery(cattery):
    cats = get_cats(cattery.id)
    return categorize_cats(cats)

@snapshot()
def get_cats(cattery_id):
    return ["Whiskers", "Chonk"]

@snapshot()
def categorize_cats(cats):
    return {"chonky": cats}

The debug file will include the complete call hierarchy with inputs and outputs for each function.

Contributing

Contributions are welcome! Please check out our Contributing Guide for details.

License

MIT License - see LICENSE