I am a beginner to python and found a code to draw triangle by Turtle as below code
def drawPolygon(t, vertices):
t.up()
(x, y) = vertices[-1]
t.goto(x, y)
t.down()
for (x, y) in vertices:
t.goto(x, y)
import turtle
t = turtle.Turtle()
t.hideturtle()
drawPolygon(t, [(20, 20), (-20, 20), (-20, -20)])
turtle.done()
1st thing I don't understand is this: (x, y) = vertices[-1].
2nd thing I don't understand is this: for (x, y) in vertices:.
In your code, vertices is a list passed into the function, so (x, y) = vertices[-1]just access the last element in the list (-1 means first from the end), and (x,y) is a tuple to store the values returned. for (x, y) in vertices: is just a way of iterating through all elements in the list vertices.
Refer these for more info:
https://docs.python.org/3/tutorial/controlflow.html
https://docs.python.org/3/reference/simple_stmts.html#assignment-statements
The first line: (x, y) = vertices[-1] is basically saying
Take the last element in list
vertices, which is(-20, -20), and assigned its elements toxandy.
So x would be equal to -20, and y would be equal to -20 as well.
The second line: for (x, y) in vertices:. That line creates a for loop.
This specific loop goes through the list vertices, and takes each value, and makes the turtle go to that value with the .goto() function.
Hope this helps!
(x, y) = vertices[-1]
The subscription of -1 means to get the last element of the array, and in this case, it's (-20, -20).
for (x, y) in vertices:
Will make python iterate through each element in the array, during each iteration, the element of the iteration is accessible by calling (x, y).