add colabturtle lesson

lessons/beginners-en/colabturtle/index.md

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+
+# 🐍 🐢
+
+In this lesson, we will be drawing with the [ColabTurtle](https://github.com/tolgaatam/ColabTurtle) module a lot.
+
+> [note]
+> In the older versions of the materials, we have used the turtle module
+> which is available in for every Python installation
+> but more and more Mac users started to have unfixable issues with it
+> so we have decided to switch to ColabTurtle that we also use for the homework
+> for this lesson.
+
+Start the Google Colab with a newly created notebook and install and initialize the ColabTurtle in a following way.
+
+First run this line in a first cell:
+
+```console
+!pip3 install ColabTurtle
+```
+
+This will install the ColabTurtle module inside your colab environment for this lesson.
+You need to do it once in every colab notebook, where you want to use it. You also need to run this cell if you close and open this colab notebook again.
+
+When this is done, you can import all functions from ColabTurtle module using this:
+
+```python
+from ColabTurtle.Turtle import initializeTurtle, forward
+```
+
+Don't worry, we will talk about the possible ColabTurtle functions throughout the lesson.
+
+Before you start using any turtle commands in a new cell, you need to initialize it by typing this:
+
+```python
+initializeTurtle()
+```
+
+Initialization means that a fresh canvas window is created below the current cell, turtle image is rotated with a head north and you can start drawing!
+
+Try moving the turtle forward by 50 units (screen pixels) by running following in a new cell:
+
+```python
+forward(50)
+```
+
+You can see that a new canvas is drawn below the current cell and the turtle is leaving a drawn line behind itself with length 50.
+
+## Rotation
+
+In order to clear the canvas for next drawing, you need to call the `initializeTurtle()` again.
+
+The turtle can rotate and crawl across the "paper".
+
+```python
+from ColabTurtle.Turtle import forward, left, right, initializeTurtle
+initializeTurtle()
+
+forward(50)
+left(60)
+forward(50)
+right(60)
+forward(50)
+```
+
+This is already really powerful way how to draw a lot of beautiful pictures.
+
+For the further steps you can freely consult the ColabTurtle API description (what each available function does and what parameters does each function have) on [https://github.com/tolgaatam/ColabTurtle#api](https://github.com/tolgaatam/ColabTurtle?tab=readme-ov-file#api).
+
+### Square
+
+Draw a square.
+
+![Turtle square](static/turtle-square.png)
+
+A square has four equal straight sides and four 90° angles.
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, left, initializeTurtle
+initializeTurtle()
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+```
+{% endfilter %}
+
+### Rectangle
+
+Draw a rectangle.
+
+Try to make it so that the turtle will "look" to the top in the end (like it was in the beginning).
+
+![Turtle rectangle](static/turtle-rect.png)
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, left, initializeTurtle
+initializeTurtle()
+forward(100)
+left(90)
+forward(50)
+left(90)
+forward(100)
+left(90)
+forward(50)
+left(90)
+
+```
+{% endfilter %}
+
+### Three squares
+
+Now draw three squares, each rotated by 20° from the previous one!.
+
+![Three turtle squares](static/turtle-squares.png)
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, left, initializeTurtle
+initializeTurtle()
+
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+
+left(20)
+
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+
+left(20)
+
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+forward(50)
+left(90)
+
+```
+{% endfilter %}
+
+### Can we write it better?
+
+So much code! There has to be a way how to simplify it.
+
+There is.
+Now we will learn the command `for`.
+
+## Repetition
+
+What does the following code do?
+
+```python
+for number in range(5):
+    print(number)
+
+for greeting in 'Ahoj', 'Hello', 'Hola', 'Hei', 'Hallo':
+    print(greeting + '!')
+```
+
+What does the command `for` do?
+
+{% filter solution %}
+The command `for` repeats part of a program.
+It repeats commands that are indented after `for`.
+It's the same as with `if` - it applies only to
+commands that are indented below.
+
+The command `for x in range(n):` repeats the commands below <var>n</var> times
+and it increments the variable `x` gradually from <var>0 to n-1</var>.
+
+The command `for x in a, b, c, d, ...:` repeats the commands below;
+it changes the variable `x` gradually to <var>a</var>, <var>b</var>,
+<var>c</var> <var>d</var>, ...
+
+In computer programming, a loop is a sequence of instructions that is continually repeated until a condition is reached.
+Very powerful concept allowing you to significantly reduce duplication of commands.
+
+{% endfilter %}
+
+### Overwriting variables
+
+What does the following program do?
+
+```python
+sum = 0
+# lets print how the sum is initialized before the loop starts
+print("sum is", sum)
+for number in 8, 45, 9, 21:
+    # internal variable inside the loop is number
+    print("number is", number)
+    sum = sum + number
+    # sum variable is holding the temporary sum of values
+    print("sum is", sum)
+print('loop ended, sum is', sum)
+```
+
+{% filter solution %}
+The command `sum = sum + number` calculates the value of
+`sum + number`, adds the current number to the sum,
+and stores the result in the variable `sum`.
+The new value of `sum` will be used in the next loop.
+
+In the beginning the sum is 0, and in the end the sum of
+our numbers will be printed.
+{% endfilter %}
+
+### Square
+
+Back to drawing! This time we will use loops.
+
+Draw a square.
+
+Use `forward` only twice, once in the import
+and once as function.
+
+![Turtle square](static/turtle-square.png)
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, left, initializeTurtle
+initializeTurtle()
+
+for i in range(4):
+    forward(50)
+    left(90)
+```
+{% endfilter %}
+
+### Discontinuous line
+
+The functions `penup` and `pendown` from the `ColabTurtle`
+module tell the turtle to stop/start drawing.
+
+Try to draw a discontinuous line.
+
+![Turtle and discontinuous line](static/turtle-dashed.png)
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, penup, pendown, initializeTurtle
+initializeTurtle()
+for i in range(10):
+    forward(10)
+    penup()
+    forward(5)
+    pendown()
+
+```
+{% endfilter %}
+
+Now try to make it so that the lines that are drawn become
+gradually bigger.
+
+![Turtle and discontinuous line]](static/turtle-dashed2.png)
+
+> [note] Help
+>
+> What exactly does the command `for` do?
+> Can we use the variable that it sets up?
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, penup, pendown, right, initializeTurtle, speed
+initializeTurtle()
+speed(5)
+right(90) # so that the drawing still fits into the canvas
+for i in range(20):
+    forward(i)
+    penup()
+    forward(5)
+    pendown()
+
+```
+{% endfilter %}
+
+>[note] Loop variable Naming
+>Always use a meaningful loop variable name, like **for index_tab_browser in range(3, 18): close_tab_in_browser(index_tab_browser) ** not just i, j, x, y etc.
+>When using meaningful names:
+> - the code is more understandable to colleagues reading your code,
+> - it's easier to find errors in the loop logic
+> - text searches for the variable name return relevant pieces of code operating on the same data are more reliable
+>
+> There is one exception - when it's a single-level loop and the variable has no meaning other than "the number of times I've been through this loop", in which case `i` is usually be used.
+
+### Three squares
+
+Finally, draw three squares, each rotated by 20°.
+Now you know how to write it in a simple way: repeat the code
+by using `for`, do not copy the same code three times.
+
+![Three turtle squares](static/turtle-squares.png)
+
+{% filter solution %}
+```python
+from ColabTurtle.Turtle import forward, left, initializeTurtle
+initializeTurtle()
+for i in range(3):
+    for j in range(4):
+        forward(50)
+        left(90)
+    left(20)
+```
+{% endfilter %}
+
+
+## Extra tasks
+
+When you are done, try to draw stairs:
+
+![Turtle stairs](static/turtle-stairs.png)
+
+When you are also done with the stairs, try to draw 7 hexagons:
+
+![Turtle hexagons](static/turtle-hexagons.png)

lessons/beginners-en/colabturtle/info.yml

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+title: Colab Turtle and loops
+style: md
+attribution:
+- Written by Lubomir Dolezal, 2024 for [PyLadies Vienna].
+license: cc-by-sa-40

runs/2024/pyladies-en-vienna-2024-spring/info.yml

@@ -107,14 +107,14 @@ plan:
   date: 2024-04-09
   slug: strings
   # materials:
-  #  - lesson: beginners-en/turtle
-  #  - lesson: beginners-en/while
-  #  - title: If/While cheatsheet
-  #    url: https://github.com/ehmatthes/pcc/releases/download/v1.0.0/beginners_python_cheat_sheet_pcc_if_while.pdf
-  #    type: cheatsheet
-  #  - title: Homework
-  #    url: https://docs.google.com/document/d/1t76R6vXagNsjPJvZz5JoQracXVq_0YLHNYDymwKOlPU/edit
-  #    type: homework
+  # - lesson: beginners-en/colabturtle
+  # - lesson: beginners-en/while
+  # - title: If/While cheatsheet
+  #   url: https://github.com/ehmatthes/pcc/releases/download/v1.0.0/beginners_python_cheat_sheet_pcc_if_while.pdf
+  #   type: cheatsheet
+  # - title: Homework
+  #   url: https://docs.google.com/document/d/1FO4J7l2oKN_vdrXVgvbrKOpJEx1Vu3f6gLnZe-tKIM4/edit
+  #   type: homework
 
 - title: Strings, Custom functions
   date: 2024-04-16