here variable is an identifier and expr is an expression the semantics of the assignment is that the expression on the right side is evaluated to produce valuewhich is then associated with the variable named on the left side here are some of the assignments we've already seenx ( xfahrenheit celsius variable can be assigned many times it always retains the value of the most recent assignment here is an interactive python session that demonstrates the pointmyvar myvar myvar myvar myvar myvar myvar the last assignment statement shows how the current value of variable can be used to update its value in this case simply added one to the previous value the chaos py program from did something similarthough bit more complex rememberthe values of variables can changethat' why they're called variables sometimes it' helpful to think of variable as sort of named storage location in computer memorya box that we can put value in when the variable changesthe old value is erased and new one written in figure shows how we might picture the effect of using this model this is exactly the way assignment works in some computer languages it' also very simple way to view the effect of assignmentand you'll find pictures similar to this throughout the book after before figure variable as box view of python assignment statements are actually slightly different from the "variable as boxmodel in pythonvalues may end up anywhere in memoryand variables are used to refer to them assigning variable is like putting one of those little yellow sticky notes on the value and saying"this