Programmieren lernen mit Python

1. 00:00Hello, everyone.
2. 00:01So far we have only dealt with text output, and today we want to deal with graphics output using Turtle.
3. 00:08Meanwhile, Simon has got to know the turtle Leonie at the holiday camp, and she loves to draw.
4. 00:15Right. Turtle's gonna be our turtle Leonie.
5. 00:19Leonie always has a pen with her, because she loves to paint.
6. 00:23So she can go forward and backward with this pen, turn to the sides or even lift and set it down again.
7. 00:31We thus give her instructions on how to move, and so graphics and pictures are created.
8. 00:38For these pictures we can paint, we have a field from -200 to 200, both in width and height.
9. 00:46Our turtle stands in the middle at the beginning, so go to point 0, 0 and look to the right.
10. 00:52She can always take a step, so this is a screen point, turn left and right, you give an angle, and the rotations always happen directly on the same spot.
11. 01:04So let's just go back to the beginning. a little more general on Turtle.
12. 01:09Turtle is a so-called library.
13. 01:13Libraries provide various functions and can actually be imagined similar to a real library, ...which is where I go in and check out different books.
14. 01:23So I can go to libraries also make use of various functions.
15. 01:27First of all, at the beginning of a program you always have to Include libraries that you want to use.
16. 01:34So now if we want to include our turtle library we write from, well from, the library turtle import, import *.
17. 01:45With this we include all functions of the library turtle.
18. 01:50However, we can also list special function names instead of this asterisk, if we only want to import certain functions.
19. 01:58The general command to include libraries means from, then the library name, import and then the different function names or an asterisk.
20. 02:08The first function we get to know from this library, means forward.
21. 02:14So move forward and in the brackets we give the number of steps, how far forward our turtle should move.
22. 02:22So here in the program we bind, as Nina has just explained, in the first line our library turtle in and all functions from it.
23. 02:30And so we can then call the function forward in the second line, with the 100 and can thus take 100 steps forward here,
24. 02:39which in this case is to the right, because our turtle starts off to the right.
25. 02:44But always just running forward is a bit boring, and therefore you can also use the library turtle to turn to the right for example.
26. 02:52So we see again our first two already known lines.
27. 02:56So we walked 100 steps, and after these 100 steps we want to turn 90 degrees to the right.
28. 03:02So we turn at right angles and then run another hundred steps forward again.
29. 03:07So in the third line we see that the function right is called, which means right and thus symbolizes a right turn,
30. 03:15and in the round brackets you always give the angle, that we want to walk or spin.
31. 03:20The angle can have a degree value between 0 and 360 degrees.
32. 03:25So if you play the whole thing once, you can see that we're walking straight ahead, turning 90 degrees and then run another 100 steps.
33. 03:33Another function is the goto function, so go to that one point.
34. 03:40Therefore we give the x- and y-coordinates, they must of course be between -200 and 200 again, so they're still in our picture.
35. 03:51So we can again include our library in line 1 and then in line 2 goto with 100 and 100.
36. 03:59So we see that our turtle runs from the starting position 0, 0 to this point.
37. 04:04But there are also the two functions penup and pendown.
38. 04:09So we include our turtle library in line 1 as usual, and if we call penup now, it means we want to lift the pen.
39. 04:18The pen is called pen and up is the lifting of the pen.
40. 04:22So we can take off with it, and now we're running at a certain point with the method just goto
41. 04:28and thus draw from the point where we started 0, 0 up to 0, -100 no line, we have lifted the pencil.
42. 04:37Now, if we want to draw, so we can put the pen down where we just got it.
43. 04:44We can do this with the method pendown.
44. 04:48After that I walk another 100 steps, so that we can also see, that we have now drawn a step.
45. 04:54So when we play the whole thing again, we'll see, we walked to a point and we didn't even see that there was a line
46. 05:00and then draw from that point because we put the pen down again, the line that is then drawn in the next 100 steps.
47. 05:08We can now combine these functions and thus create different shapes and patterns.
48. 05:15As you can see right here, for example, we have called the function forward four times, each time with 100 steps, and in between always the function right with 90, so always a 90 degree turn to the right.
49. 05:29And so you may already have guessed, a square is created.
50. 05:32As you can also see here, we start by walking 100 steps and then turn and run 100 paces again and keep rotating until we finish the square.
51. 05:43So you can give free rein to your creativity and paint many different shapes.
52. 05:49So we've learned, how to use and integrate libraries.
53. 05:52We have particularly focused on the turtle library and various functions such as forward and goto from this library.
54. 06:01In the next video we will learn more about this library, and you can already give free rein to your creativity and try out different things with it.

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