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# Context and Globals
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Flask provides context management and global objects for accessing application and request data throughout the request lifecycle.
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## Capabilities
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### Context Management Functions
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```python { .api }
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def has_app_context() -> bool:
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    """Check if there is an active application context."""
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def has_request_context() -> bool:
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    """Check if there is an active request context."""
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def copy_current_request_context(f: Callable) -> Callable:
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    """Copy the current request context for use in a different thread."""
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def after_this_request(f: Callable) -> Callable:
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    """Register a function to run after the current request."""
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```
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### Global Proxy Objects
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```python { .api }
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current_app: LocalProxy  # Current Flask application
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request: LocalProxy      # Current request object
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session: LocalProxy      # Current session
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g: LocalProxy           # Application context global object
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```
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### Context Classes
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```python { .api }
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class AppContext:
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    """Application context for Flask applications."""
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class RequestContext:
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    """Request context for handling individual requests."""
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```
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## Usage Examples
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### Basic Context Usage
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```python
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from flask import Flask, current_app, request, g
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app = Flask(__name__)
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@app.before_request
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def before_request():
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    g.user_id = request.headers.get('X-User-ID')
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@app.route('/context-info')
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def context_info():
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    return {
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        'app_name': current_app.name,
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        'request_method': request.method,
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        'user_id': g.get('user_id')
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    }
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```