Add a "scripting" reading exercise

Author: James Collier

dodona/reading-exercises/scripts/config.json

@@ -0,0 +1,14 @@
+{
+  "description": {
+    "names": {
+      "en": "Scripting"
+    }
+  },
+  "labels": [
+    "real-world programming"
+  ],
+  "internals": {
+    "token": "X5rVj9e4R7tbj4SxX78RXrS93eTq5CkKfT6HWTJrer2I-N33yqry9dj-nSRfzHct",
+    "_info": "These fields are used for internal bookkeeping in Dodona, please do not change them."
+  }
+}

dodona/reading-exercises/scripts/description/description.en.md

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+When you write a program for yourself (or download a Python program from the internet), you will
+probably want to run it sooner or later.
+
+This is quite straightforward. You can simply follow these steps:
+* Open the terminal program you use (on Windows this might be called "Power Shell" or "CMD"),
+* Navigate to the folder where the program is stored,
+* Run the program by typing `python my_cool_program.py` (also known as running a "script").
+
+There is an important problem when building programs that you should be aware of: any top-level code
+always runs when you run the script **BUT ALSO** at _import_ time. That's right! You can `import`
+your program too.
+
+This is a problem because, you probably don't expect to be running Python code just because you
+`import`ed something. To avoid this you can use a trick to check if your code is being run as a script
+or if it's being imported.
+
+There is a special variable that Python gives you called `__name__` which is the name of the current
+module. Try this in your own programming environment if you like: create 2 files.
+
+A file "a.py" should contain:
+```python
+print("__name__ is: ", __name__)
+```
+
+A file "b.py" should contain:
+```python
+import a
+print("I'm in b")
+```
+
+Now run `python a.py` (Use a.py as a script, not importing it). This should be printed to the console:
+```
+__name__ is:  __main__
+```
+
+And if you run `python b.py` (Import a.py). This should print:
+```
+__name__ is:  a
+I'm in b
+```
+
+Notice that the special variable `__name__` contains `"__main__"` when you run the file as a script.
+So when you define code to run when using your program as a script you should use this construction:
+```python
+if __name__ == "__main__":
+   # code to run when using my program as a script.
+
+```
+