Coding classes in Saxony-Anhalt

Gymnasien and cooperative Gesamtschulen finish after twelve years (G8): the Einführungsphase is grade 10 and the two Qualifikationsphase years are 11 and 12. At the integrated Gesamtschule and the Gemeinschaftsschule the Abitur usually comes after grade 13. With only two hours a week in the Oberstufe, a pupil who wants to study computer science later usually needs far more practice than school can give.

import csv

with open("radrouten_ueberregional.csv", encoding="utf-8") as f:
    sections = list(csv.DictReader(f, delimiter=";"))

longest = max(sections, key=lambda s: float(s["laenge_m"]))
print("Sections:", len(sections))
print("Longest single section:", longest["route"], round(float(longest["laenge_m"]) / 1000, 1), "km")

One section of the Altmarkrundkurs, the circular route through the Altmark in the north of the Land, is stored as a single 346.7 km piece. That says something about how the data was drawn, not about which route is longest. Version 2 groups sections by route name and adds their lengths.

from collections import defaultdict

per_route = defaultdict(float)
for s in sections:
    per_route[s["route"]] += float(s["laenge_m"]) / 1000

ranking = sorted(per_route.items(), key=lambda item: item[1], reverse=True)
print("Routes:", len(per_route))
for name, km in ranking[:3]:
    print(" ", name, round(km, 1), "km")

Now the 678 rows have become 23 routes, and the Altmarkrundkurs leads with 518.3 km. But adding everything counts alternatives and detours too, as if a cyclist rode both ways round a closed bridge. Version 3 looks at the category labels first.

labels = defaultdict(int)
for s in sections:
    labels[s["kategorie"] or "(empty)"] += 1
print("Category labels:", dict(labels))

main_only = defaultdict(float)
for s in sections:
    if s["kategorie"] in ("Hauptroute", ""):
        main_only[s["route"]] += float(s["laenge_m"]) / 1000
elbe = "Elberadweg (ERW)"
print("Elberadweg, all rows:", round(per_route[elbe], 1), "km; without detours and variants:", round(main_only[elbe], 1), "km")

Data: Ministerium für Infrastruktur und Digitales Sachsen-Anhalt, WFS ST Radwegenetz ALRIS, layer überregionale touristische Radrouten, Datenlizenz Deutschland Namensnennung 2.0, retrieved 3 November 2026. Lengths are the section lengths stored in the data; the sums, rankings and the choice to treat unlabelled rows as main route are our own.

Half of all rows have no category, and Version 3 has to make a choice about them: here we treat them as main route, and say so. For the Elberadweg the answer moves from 237.7 km with every row to 131.1 km without alternatives, side routes and detours. Neither number is "the length of the Elberadweg"; each is the length of a clearly defined set of rows. That is the lesson: group first, then define what you count, and print the definition next to the number.

1. Ages 9 to 11, no screen. Cut a long strip of paper into five pieces of different lengths and label two of them "detour". Measure the longest piece, then the whole route with and without detours.
2. Ages 11 to 13, Scratch. Store pairs of route name and length in two lists, add up the lengths for each name, and show the longest route.
3. Teenagers, Python. Run Version 1 and Version 2 and explain why their winners differ. Then change Version 3 to treat unlabelled rows as not counted and compare.
4. Going further. Rank all 23 routes by main-route length only, and write one sentence for each of the top three that says exactly which rows were counted.