# Phoenix Tracing: Projects (Python)
**Organize traces by application using projects (Phoenix's top-level grouping).**
## Overview
Projects group traces for a single application or experiment.
**Use for:** Environments (dev/staging/prod), A/B testing, versioning
## Setup
### Environment Variable (Recommended)
```bash
export PHOENIX_PROJECT_NAME="my-app-prod"
```
```python
import os
os.environ["PHOENIX_PROJECT_NAME"] = "my-app-prod"
from phoenix.otel import register
register() # Uses "my-app-prod"
```
### Code
```python
from phoenix.otel import register
register(project_name="my-app-prod")
```
## Use Cases
**Environments:**
```python
# Dev, staging, prod
register(project_name="my-app-dev")
register(project_name="my-app-staging")
register(project_name="my-app-prod")
```
**A/B Testing:**
```python
# Compare models
register(project_name="chatbot-gpt4")
register(project_name="chatbot-claude")
```
**Versioning:**
```python
# Track versions
register(project_name="my-app-v1")
register(project_name="my-app-v2")
```
## Switching Projects (Python Notebooks Only)
```python
from openinference.instrumentation import dangerously_using_project
from phoenix.otel import register
register(project_name="my-app")
# Switch temporarily for evals
with dangerously_using_project("my-eval-project"):
run_evaluations()
```
**⚠️ Only use in notebooks/scripts, not production.**
