whytrace 0.1.2

A conditional logic visualizer for Python

whytrace

Explain and visualize why your Python function took a particular control-flow path for a given set of inputs.

whytrace helps evaluate your if / elif / else conditions (including short-circuiting and/or), and renders a rich, human-friendly decision tree. It also steps through for and while loops, showing per-iteration state and flow-control (break, continue, pass) so you can quickly see what executed and why.

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Features

• Decorator-based: Add @why and call your function as usual.
• Rich console tree: Clear, colorized decision diagrams using rich.
• Condition insight: Shows boolean short-circuiting (and/or) step-by-step.
• Flow control: Displays break, continue, and pass exactly where they occur.
• Zero app logic changes: Your function still runs and returns its normal result.

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Installation

This project currently targets Python 3.9+

pip install whytrace

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Quickstart

from whytrace import why

@why
def check_user(user):
    if user["is_active"] and user["age"] > 18:
        if user["age"] > 21:
            return "ALLOW"
    else:
        return "DENY"

result = check_user({"is_active": False, "age": 16})
print("Result:", result)

Example console output (trimmed):

check_user()
└── if user["is_active"] and user["age"] > 18
    ├── user["is_active"] → ❌
    └── ⛔ Short-circuited at user["is_active"]
└── else

Conditional Looping

@why
def process(items, user):
    for i in items:
        if user["active"] and i > 3:
            print("Active user")
        elif user["banned"]:
            print("blocked")
            continue
        else:
            print("skip")


process(
    items=[1, 4, 7],
    user={"active": True, "banned": True},
)

Example console output (trimmed):

process()
└── for i in items
    ├── iteration 0 → i = 1
    │   ├── if user['active'] and i > 3
    │   │   ├── user['active'] → ✅
    │   │   ├── i > 3 → ❌
    │   │   └── ⛔ Short-circuited at i > 3
    │   └── elif user['banned'] → ✅
    │       ├── continue
    │       └── ↩ continue to next iteration
    ├── iteration 1 → i = 4
    │   └── if user['active'] and i > 3
    │       ├── user['active'] → ✅
    │       └── i > 3 → ✅
    └── iteration 2 → i = 7
        └── if user['active'] and i > 3
            ├── user['active'] → ✅
            └── i > 3 → ✅
blocked
Active user
Active user

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More Examples

Nested conditionals

See examples/nested.py:

from whytrace import why

@why
def access_control(user, resource):
    if user["active"]:
        if resource["public"]:
            print("Access granted")
        elif user["role"] == "admin":
            print("Admin access")
        else:
            print("Access denied")
    else:
        print("Inactive user")

access_control(
    user={"active": True, "role": "user"},
    resource={"public": False}
)

Loops, break/continue/pass

See examples/loop.py:

from whytrace import why

@why
def process(items, user):
    for i in items:
        if user["active"] and i > 3:
            print("Active user")
        elif user["banned"]:
            print("blocked")
        else:
            print("skip")

process(
    items=[1, 4, 7],
    user={"active": True, "banned": True},
)

Note : Checkout examples folder for further examples

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Supported Constructs

• if / elif / else
• Boolean operations: and, or (with explicit short-circuit visibility)
• for loops (per-iteration state shown)
• Flow nodes: break, continue, pass

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CLI-Free: Just Run Your Script

The easiest way to use whytrace is to decorate functions in your code and run your script normally:

python examples/credit_score.py
python examples/feature_flag.py
python examples/loop.py
python examples/multi_layer.py
python examples/nested.py

You’ll see a rich tree printed before the function’s return value.

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Contributing

Ideas and PRs welcome! Useful areas to explore:

• Support for try/except and additional control structures.
• Support for switch , goto etc
• Configurable while iteration caps.
• Safer evaluation strategies and richer context controls.
• Output adapters (e.g., HTML export) in addition to the console tree.