Online Python classes in Bottrop

import csv

with open("schulen_nrw.csv", encoding="utf-8") as f:
    schools = list(csv.DictReader(f))
print("Step 1, all schools in NRW:", len(schools))

bottrop = [s for s in schools if s["municipality"] == "05512000"]
print("Step 2, in Bottrop:", len(bottrop))

upper = [s for s in bottrop if s["school_type"] in ("15", "20")]
print("Step 3, Gesamtschule or Gymnasium:", len(upper))

Each count can be checked by eye. Thirty-two entries in Bottrop, including primary schools and a few that are not schools at all, such as the school supervision office, which has its own type code. Five of them are a Gesamtschule or a Gymnasium. Now the second file: keep only the courses of those five, then narrow down to Informatik, then to Leistungskurs.

numbers = {s["school_no"] for s in upper}
with open("kurse_nrw.csv", encoding="utf-8") as f:
    courses = [c for c in csv.DictReader(f) if c["school_no"] in numbers]
print("Step 4, schools with any Oberstufe course listed:", len({c["school_no"] for c in courses}))

informatik = [c for c in courses if c["subject"] == "IF"]
print("Step 5, offering Informatik:", len({c["school_no"] for c in informatik}))

lk = [c for c in informatik if c["lk_q1"] == "1" or c["lk_q2"] == "1"]
print("Step 6, offering it as Leistungskurs:", len({c["school_no"] for c in lk}))

Files from the NRW Ministerium für Schule und Bildung (Schulgrunddaten NRW; Kursangebot in der gymnasialen Oberstufe), Datenlizenz Deutschland Namensnennung 2.0, retrieved on 3 November 2026; every count here is our own. The ministry notes that schools may offer further subjects through cooperations not listed here, and that the data come from the previous year's survey, with 15 October as the reference date.

That last note matters more than any line of code. Step 6 says 0, but the file only lists what each school offers itself; a cooperation with a neighbouring school could add a Leistungskurs that the file never shows. A careful analyst reports "none listed in the ministry file" rather than "impossible in Bottrop". Across the whole of NRW the same file lists Informatik at 654 of 956 schools with Oberstufe courses, and as a Leistungskurs at 109.

1. Younger pupils. Before running anything, guess the count after each step and write it down. Which guess was furthest off?
2. Teenagers. Change the subject code from IF to another subject you take, and run the funnel again. At which step does your subject drop out, if it does?
3. Adults. Wrap the six steps in a function that takes a municipality code and a subject code, then run it for Bottrop and two neighbouring cities and print one line each.