Add up a year of Hagen rainfall in Python and you can get 970.9999999999999 millimetres instead of 971. Nothing is broken; that is how computers store decimals, and it is exactly the kind of thing a learner alone with a video never notices. Our live online Python classes put a mentor beside you, in English, to catch it. This page explains what that looks like, how Informatik works in North Rhine-Westphalia up to an Abitur written without a computer, and the Hagen rain project in full.
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The answer first
Modern Age Coders teaches online Python classes for Hagen as live video lessons in English: a mentor follows what each learner types and makes sure they understand why the code works. There are separate courses for children from 9, for Oberstufe pupils facing the Informatik Abitur and for adults, each taught by one regular mentor to a batch of fifteen to twenty people or to a single learner.
Choose a starting course
Which Python course fits a Hagen learner?
One for children, one for Oberstufe pupils heading for an Informatik exam, and one for anyone from 13 who wants a recognised Python qualification to aim at.
What does a live mentor add to learning Python online?
Videos explain. A mentor notices. Most of what goes wrong for a beginner is something only a person watching would notice.
What tends to happen to a beginner, alone and with a live mentor (from our classes)
Moment
Alone with a video
With a live mentor
First error message
Copied into a search engine, often misread
Read aloud together, line number first
Indentation slip
Program silently does the wrong thing
Spotted on the shared screen within seconds
A strange decimal like 970.9999999999999
Assumed to be a bug in Python
Explained: how computers store decimals
Stuck for twenty minutes
The evening ends there
One question from the mentor unblocks it
Code that works
Moved on from
Explained back in the learner's own words
Our own observations from teaching live classes, not a study. The decimal row is the subject of the Hagen project below.
Concretely: sixty minutes of video call, one screen shared at a time. The learner types in their own editor on their own computer; the mentor sees it, asks questions and only very rarely takes over the keyboard. Between classes there is one short task. In a batch, learners share their screens in turn, so a mistake one person makes becomes a lesson for everyone.
In English, at your pace
Every class is taught in English by mentors based in India. We offer no lessons in German, and we say so before anyone books.
Mentors speak calmly, rephrase, and get used to each learner's accent. Since Python's keywords and error messages are English anyway, the class and the code speak the same language.
What you need
A laptop or desktop computer, a stable connection and a headset. Python costs nothing; setting it up is the first job you and your mentor do together.
A tablet is fine for a ten year old watching Scratch, but Python needs a real keyboard.
NRW schools and the Abitur
How does Informatik work in Hagen schools, up to the Abitur?
It starts early, in grades 5 and 6 for every pupil, and it ends on paper: NRW's written Informatik Abitur uses no computer.
According to the Informatik-Monitor 2026/27 of the Gesellschaft für Informatik, Informatik is required in grades 5 and 6 at every general school type in North Rhine-Westphalia. In the Oberstufe it can be taken as a three-hour Grundkurs from the Einführungsphase and, in the Qualifikationsphase, either as a three-hour Grundkurs or a five-hour Leistungskurs.
The written Informatik Abitur in North Rhine-Westphalia
Question
What the GI reports
Who sets the tasks?
The Land, centrally, the same for every school
How many tasks?
One set of four for the Grundkurs and one of four for the Leistungskurs
Who chooses?
The teacher picks two of the four in a Grundkurs and three in a Leistungskurs; pupils do not choose
Is a computer used?
No: "Der Einsatz eines Computers ist für die Bearbeitung der schriftlich Abituraufgaben nicht vorgesehen."
Which aids?
A German spelling dictionary and a scientific calculator or CAS
Written or oral?
Always written in a Leistungskurs; written or oral in a Grundkurs
Quoted and summarised from the GI's Informatik-Monitor 2026/27, NRW entry, as published on 2 November 2026 when we read it.
A paper exam changes how you should learn to program. With no computer to run the code, a pupil must predict what it does: trace the loop, track every variable, know what a number will look like. That is why our Python classes ask learners to predict output before they run anything, and why the rain project below is a good exam habit as much as a coding one. We teach alongside the school course and award no grades; the school's Informatik is the one that counts. Our Informatik Abitur in NRW page goes deeper.
A real Hagen project
Why does Python say Hagen had 970.9999999999999 mm of rain?
A simple question, how much rain fell in a year, leads straight to one of the most useful lessons in programming.
The data
Between June 1978 and December 2007 the Deutscher Wetterdienst operated a station named Hagen-Fley. Its day-by-day observations are open data (CC BY 4.0: reuse is fine as long as the DWD is credited), and our copy dates from 3 November 2026.
From it we made hagen_regen.csv: one row per day from 1 January 1979 to 31 December 2007, 10,592 days, with the date and the rainfall in millimetres, always written with one decimal place, such as 2.2.
The question
Which year was the wettest, and how much rain fell in 1987? Version 1 adds up each year's daily values as ordinary decimal numbers (floats) and prints the totals.
It also asks a yes-or-no question that looks too easy to fail: was 1987's total exactly 971.0 mm?
Version 1: add the decimalsPython
import csv
rain = {}
with open("hagen_regen.csv", encoding="utf-8") as f:
for rec in csv.DictReader(f):
year = rec["datum"][:4]
rain[year] = rain.get(year, 0) + float(rec["regen_mm"])
wettest = max(rain, key=rain.get)
print("Wettest year:", wettest, rain[wettest], "mm")
print("1987 total:", rain["1987"])
print("Was 1987 exactly 971.0 mm?", rain["1987"] == 971.0)
It prints: Wettest year: 1981 1201.2999999999988 mm, 1987 total: 970.9999999999999 and Was 1987 exactly 971.0 mm? False.
Every daily value had one decimal place, so every total should too. Instead Python prints 1201.2999999999988 and 970.9999999999999, and the comparison with 971.0 says False. The reason is that a computer stores numbers in binary, and most decimal fractions, 0.1 among them, have no exact binary form, the way one third has no exact decimal form. Each value is stored as the nearest possible binary number, and after 365 additions the tiny differences show. Try it yourself: in Python, 0.1 + 0.2 prints 0.30000000000000004.
The fix is to count in whole numbers. Every value in this file is given to a tenth of a millimetre, so Version 2 turns each day into an integer number of tenths (2.2 becomes 22), adds integers, which a computer does exactly, and divides by 10 only once, when printing.
Version 2: add below Version 1, count in tenthsPython
tenths = {}
with open("hagen_regen.csv", encoding="utf-8") as f:
for rec in csv.DictReader(f):
year = rec["datum"][:4]
tenths[year] = tenths.get(year, 0) + round(float(rec["regen_mm"]) * 10)
wettest = max(tenths, key=tenths.get)
print("Wettest year:", wettest, tenths[wettest] / 10, "mm")
print("1987 total:", tenths["1987"] / 10)
print("Was 1987 exactly 971.0 mm?", tenths["1987"] == 9710)
print("Years over 1,000 mm:", sorted(y for y in tenths if tenths[y] >= 10000))
The new lines it prints: Wettest year: 1981 1201.3 mm, 1987 total: 971.0, Was 1987 exactly 971.0 mm? True and Years over 1,000 mm: ['1981', '1984', '1986', '1993', '1998', '2002', '2007'].
Yearly rainfall at Hagen-Fley: float totals against integer tenths (our calculation)
Year
Adding floats
Adding tenths
1981
1201.2999999999988
1201.3
1987
970.9999999999999
971.0
1989
767.3999999999996
767.4
1991
754.3000000000003
754.3
2003
719.8
719.8
Rain values: DWD, station 01920 Hagen-Fley, RSK (precipitation per day), years 1979 to 2007, CC BY 4.0, file taken on 3 November 2026. We wrote the code and did the adding; seven of the 29 years passed 1,000 mm. The DWD is not involved in our classes.
Look at 2003: the float total happens to come out as exactly 719.8. That is the dangerous part. The error is not always visible, so a program that seems to work on one year can fail on the next. The rule that follows is short: never compare two floats with ==, and when you need exact sums of decimal values, count in whole units.
Ages 9 to 12. Add 0.1 to a variable ten times in a loop and print it after every step. At which step does it first look strange?
Teenagers. Without running it, predict whether round(970.9999999999999, 1) == 971.0 is True. Then check. Why is rounding a fix for printing but a weak fix for comparing?
Adults. Rewrite Version 1 using math.fsum on a list of each year's values, and compare its 1987 result with both versions on this page.
Exam practice. On paper, trace a loop that adds 0.5 four times. Then explain why 0.5 behaves perfectly when 0.1 does not.
From first line to exam level
What is the Python path for a Hagen learner?
Our sequence, with the habit each stage builds. Children move through it slowly with games; teenagers and adults faster with data.
Our Python path and the habit behind each stage (ours)
Stage
Content
Habit
1
print, variables, arithmetic
Predict before you run
2
if, for, while
Trace the loop by hand
3
Lists and dictionaries
Choose the right container
4
Functions
Write it once, test it twice
5
Files and real data
Check what the data really contains
6
Numbers inside the machine
Know what a float can and cannot hold
7
Projects and exam tasks
Explain every line in words
Our own outline. Abitur pupils work through stages 1 to 7 with Java alongside Python, as the Informatik Abitur course does.
Stage 6 is where many self-taught programmers have a gap. It looks like trivia until a bank balance, a grade average or a sensor total goes subtly wrong. For pupils facing a paper exam it is also the stage that makes predictions reliable: if you know that 0.1 is stored inexactly, you will not be surprised by the output you are asked to predict.
Times and holidays
When are live Python classes for Hagen learners?
Weekdays or weekends, flexible: choose your batch, or for a very personalised plan choose 1-on-1 at your convenience, weekend mornings or weekdays.
Example Hagen times and the mentor's local time
Hagen
India, to 28 March 2027
India, from 28 March 2027
15:35
20:05
19:05
17:40
22:10
21:10
Saturday 12:30
17:00
16:00
Sunday 09:30
14:00
13:00
Germany switches between MEZ, UTC+1, and MESZ, UTC+2, under the Einheitenzeitgesetz; the latest switch to MEZ was on 25 October 2026 and the next to MESZ is on 28 March 2027. India does not switch (UTC+5:30), so its clocks run four hours thirty ahead of Hagen in winter and three hours thirty in summer. Batch times are agreed, not fixed.
School holidays in North Rhine-Westphalia for 2026/27, from the KMK overview dated 9 October 2025: autumn from 17 to 31 October 2026; Christmas from 23.12.2026 to 06.01.2027; Easter from 22 March to 3 April 2027; a single Whitsun day on 18 May 2027; and summer from 19 July to 31 August 2027. Classes carry on through all of them unless you choose to pause.
Hagen's population on 31 December 2024 was 190,384, by the Destatis count; North Rhine-Westphalia as a whole had 18,034,454. Learners from Dortmund (603,462), Bochum (358,676) or Wuppertal (358,193) are also in North Rhine-Westphalia and share the same school calendar and the same central Abitur.
Checks of understanding
How do we know a Python learner really understands?
Five checks we use in class. Each one is a small task, not a test score.
Five checks of understanding (ours)
Check
The learner can
Prediction
Write down the output of a short program before running it
Tracing
Fill in a table of variable values for each loop step on paper
Error reading
Find the failing line from a traceback alone
Number sense
Explain why 0.1 + 0.2 is not printed as 0.3
Explanation
Describe a program they wrote in five plain sentences
For Abitur pupils
Prediction and tracing are exactly what a paper exam rewards. We practise them on every program, not only before exams.
Number sense often decides the last marks on a tracing task.
For adults
Number sense is the check most professionals have never been taught. It matters the moment Python touches money or measurements.
Bring a spreadsheet from work and we will test it with you.
Other courses
Nine more courses for Hagen learners
Some come before Python, some beside school, some after the first course.
I
Younger learners
Ages 6 to 16
PYH / YOUNG / 01
Scratch first
Block coding for children not yet typing, 6 to 12.
A weather forecasting site with live conditions for any location.
by Krish
Fees
What do online Python classes cost in Hagen?
One fee per month, eight live classes. The euro amount on this page is calculated with the European Central Bank reference rate, but payment is taken in US dollars, so your bank converts it and its euro figure can be a little different from ours.
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Hagen asks
Online Python classes in Hagen: common questions
Are the Python classes in German?
No, English is the only teaching language. Mentors work from India and fit their speed and wording to each learner. Python's own keywords and error messages are English, so the language of the class matches the language of the code.
Are the classes live?
Yes. A mentor is on the video call for the full hour, sees the learner's shared screen and helps in the moment. There are no pre-recorded lessons in place of the mentor.
Is the Informatik Abitur in NRW written on a computer?
No, it is a paper exam: the GI states that no computer is used for the written Informatik papers in North Rhine-Westphalia. The Land sets the tasks, and the teacher chooses two of four in a Grundkurs and three of four in a Leistungskurs.
Do NRW pupils learn Informatik before the Oberstufe?
Yes. Grades 5 and 6 include required Informatik at all general schools, and electives follow later, differing by school type.
When can I take classes in Hagen time?
Weekdays or weekends, flexible: choose your batch, or for a very personalised plan choose 1-on-1 at your convenience, weekend mornings or weekdays. Pupils often choose late afternoons, adults evenings or weekend mornings.
What is the rain project on this page?
A lesson we built from Hagen-Fley rainfall published by the Deutscher Wetterdienst, 1979 to 2007. Adding the daily values as floats gives 970.9999999999999 mm for 1987; counting in whole tenths of a millimetre gives exactly 971.0.
Why does 0.1 + 0.2 not equal 0.3 in Python?
Because Python stores such numbers in binary, and 0.1 and 0.2 have no exact binary form. Each is stored as the nearest possible value, so the sum prints as 0.30000000000000004. Compare floats with a tolerance, or count in whole units.
Can my child learn Python online?
From about 9, yes, in our Python and AI for Kids course. Younger children usually start with Scratch, where blocks replace typing.
How big are the classes?
Batches run with fifteen to twenty learners matched by age and level; with one-to-one there is nobody else, just the learner and the mentor twice a week.
How do I pay?
Each month. The euro price you see uses the European Central Bank reference rate; the money moves in US dollars, and your bank turns that into euro, so a few cents can differ. The trial costs nothing and needs no card details.
Further pages
Related pages
More for Python learners in Hagen and North Rhine-Westphalia.
Let us know how old the learner is and what the aim is: a first program, the Abitur, or something for work. The free hour gets Python running and tries one small task; after it you hear which course and which format we suggest.
All classes are live online and only in English, with mentors in India. Message us on WhatsApp for the quickest reply, in English.
Want a class sooner? Book a priority demo
A priority demo is a full class of about 45 to 60 minutes. After the class the mentor sends a written skill report and a personal learning roadmap on WhatsApp. If you enrol, the demo fee is adjusted against your first month's fee. Share your demo Order ID with us on WhatsApp and we take it off.
