Cursor and event handling in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of event handling in matplotlib?

Event handling allows you to respond to user actions like mouse clicks, movements, or key presses on a plot, making the plot interactive.

beginner

How do you connect an event handler function to a matplotlib figure?

Use the figure.canvas.mpl_connect(event_name, handler_function) method, where event_name is the event type like 'button_press_event'.

intermediate

What information does the event object provide in a matplotlib event handler?

The event object gives details like mouse position (event.xdata, event.ydata), which mouse button was pressed, and the figure or axes involved.

beginner

What is a cursor in matplotlib and how is it useful?

A cursor is a visual tool that follows the mouse pointer on a plot, often showing crosshairs or coordinates to help users read data values precisely.

intermediate

How can you create a simple crosshair cursor that moves with the mouse in matplotlib?

By connecting a motion_notify_event to a function that updates vertical and horizontal lines at the mouse position and then redraws the canvas.

Which method connects an event handler to a matplotlib figure?

A figure.canvas.mpl_connect()

B figure.add_event_listener()

C plt.connect_event()

D canvas.attach_handler()

The correct method is figure.canvas.mpl_connect() to link events to handlers.

What event name is used to detect mouse movement in matplotlib?

A motion_notify_event

B key_press_event

C button_press_event

D mouse_move_event

The event motion_notify_event tracks mouse movement over the figure.

In an event handler, which attribute gives the x-coordinate of the mouse in data units?

A event.x

B event.xdata

C event.xpos

D event.data_x

event.xdata provides the x-position in data coordinates.

What does a cursor typically display on a matplotlib plot?

A The plot title

B The axis labels

C The legend

D Crosshairs or coordinates at the mouse position

A cursor shows crosshairs or coordinates to help read data values.

Which event would you use to detect a mouse click on a matplotlib plot?

A key_press_event

B motion_notify_event

C button_press_event

D mouse_click_event

The button_press_event detects mouse clicks.

Explain how to create an interactive cursor in matplotlib that updates as the mouse moves.

Think about how to track mouse movement and update visuals.

Describe the role of the event object in matplotlib event handling and what key information it provides.

Focus on what data the event object carries for interaction.