Variables: give a value a name
A variable is how a program remembers things. Give a value a name once. Then use it, or change it, on any line below.
The big idea
A variable holds a value under a name. Your program can use that value later, or swap it for a new one.
See it in code
The name goes on the left, then =, then the value to keep. After that, the name stands in for the value:
cookies = 12
print("Cookies left:", cookies)Cookies left: 12
cookies has no quotes around it, so Python doesn't print the word. It looks inside the variable and prints what it finds there.
A variable can change. The third line reads the old number, takes one away, and stores the answer back under the same name:
cookies = 12
print("Cookies left:", cookies)
cookies = cookies - 1
print("Cookies left:", cookies)Cookies left: 12 Cookies left: 11
A cookie sold, so the count dropped. Both print lines are the same. They show two numbers because the variable changed in between.
In the paint studio a variable is called a jar. Here one jar, sun_y, holds how far down the sun sits, and two shapes read it:
sun_y = 150
paper("light salmon")
circle(x=200, y=sun_y, size=130, color="light yellow")
circle(x=200, y=sun_y, size=90, color="gold")
rect(x=200, y=300, width=400, height=200, color="turquoise")
The glow and the sun share one jar, so they sit together. Change the jar and both shapes move at once. They both read the same number.
Every program leans on variables. A bakery keeps its prices in them. A painting keeps its sizes in them. A game keeps its score in one.
Try it yourself
Change sun_y = 150 to sun_y = 60 and run it: the sun rises. Then make a second jar, sun_x, and use it for both circles' x. Now two numbers move your whole sun.
The common mistake
Using a variable before it exists. Lines run from top to bottom, so print(cookies) placed above cookies = 12 stops with a NameError. Make the variable first, then use it.
What it unlocks
Once values have names, you can do math with them, drop them into sentences with f-strings, and keep a running total inside a loop.