CODEWITHSUNDEEP
pythonpython-3.xturtle-graphicspython-turtle
Pipo
Pipo

Reputation: 309

Draw Triangle by turtle

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:.

Upvotes: 2

Views: 3097

Answers (3)

10 Rep
10 Rep

Reputation: 2270

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 to x and y.

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!

Upvotes: 1

Red
Red

Reputation: 27567

(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).

Upvotes: 1

Zircoz
Zircoz

Reputation: 512

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

Upvotes: 2

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