yview

(#<widget> 'yview ?args?)
This command is used to query and change the vertical position of the information displayed in the canvas's window. It can take any of the following forms:
(#<widget> 'yview)
Returns a list containing two elements. Each element is a real fraction between 0 and 1; together they describe the vertical span that is visible in the window. For example, if the first element is .6 and the second element is 1.0, the lowest 40% of the canvas's area (as defined by the -scrollregion option) is visible in the window. These are the same values passed to scrollbars via the -yscrollcommand option.
(#<widget> 'yview 'moveto fraction)
Adjusts the view in the window so that fraction of the canvas's area is off-screen to the top. Fraction is a fraction between 0 and 1.
(#<widget> 'yview 'scroll number what)
This command adjusts the view in the window up or down according to number and what. Number must be an integer. What must be either units or pages. If what is units, the view adjusts up or down in units of the yScrollIncrement option, if it is greater than zero, or in units of one-tenth the window's height otherwise. If what is pages then the view adjusts in units of nine-tenths the window's height. If number is negative then higher information becomes visible; if it is positive then lower information becomes visible.

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