Python course for Peru, live and in English

Younger children are welcome too, but they need a different course: under 13 we start with Scratch or with Python for kids, using games and drawings. For learners who would rather read about this in Spanish, our Spanish page curso de Python en inglés explains the same classes from a different angle; the lessons themselves are always in English.

What every learner shares is the format. Each class is a live video lesson with a mentor based in India, who speaks clear, unhurried English and stops to check that the idea has landed before moving on. Learners type from the first class. Nobody sits and watches a recording.

1. Values and names. Numbers, text, true and false; storing them in variables; printing them. The first surprise, that 0.1 + 0.2 is not quite 0.3, arrives early, and the lesson further down this page is built on it.
2. Decisions and repetition. if, elif, else, for and while, practised on small problems the learner can check by hand before running.
3. Functions. Breaking a problem into named pieces, each with one job and a test the learner writes themselves.
4. Collections. Lists, dictionaries, tuples and sets, and choosing the right one: counting things, grouping them and looking them up quickly.
5. Files and errors. Reading and writing text and CSV files, and handling mistakes in the data instead of crashing on them.
6. Objects. Classes, methods and why programs get organised this way once they grow past a few hundred lines.
7. Libraries. Installing and using other people's code safely: data tools for analysts, web frameworks for builders, automation tools for office work.
8. A real project. Something the learner designs, builds, tests and explains in English to their mentor, from a game to a report generator to a small AI model.

ticks = 0.0
for _ in range(10):
    ticks += 0.1
print(ticks)
print(ticks == 1.0)
print(round(0.5), round(1.5), round(2.5), round(3.5))

import math
from decimal import Decimal

ticks = 0.0
for _ in range(10):
    ticks += 0.1
print(math.isclose(ticks, 1.0))

exact = sum([Decimal("0.1")] * 10)
print(exact, exact == Decimal("1.0"))
print(0.1 + 0.2, Decimal("0.1") + Decimal("0.2"))
print(Decimal(0.1))

The fix depends on the job. For a stopwatch, a physics result or anything measured, compare with math.isclose, which accepts a tiny difference. For money and anything else where every digit must be exact, build the numbers with Decimal from text, as in Decimal("0.1"). The last line of Version 2 is the one learners remember: build a Decimal from the float 0.1 instead of the text "0.1", and you get the long tail that the float was hiding all along.

None of this is special to Python. Java, C++ and spreadsheets store decimals the same way. A learner who understands this lesson stops trusting == on decimals in every language, and that one habit prevents a whole family of bugs at university and at work.

1. Predict first. Before running Version 1, write down what you expect each line to print. Most people get the first two wrong.
2. Change the step. Try 0.5 and 0.25 instead of 0.1. Both give exactly 1.0 after the right number of ticks. Explain why, using the word "binary".
3. Find the halfway cases. Print round(x) for 4.5, 5.5 and 6.5, and predict each answer before you run it.
4. Write it up. In three English sentences, tell a classmate when you would use isclose and when you would use Decimal.

Source: IANA time zone database, zones America/Lima (five hours behind UTC, with no daylight saving since 1994) and Asia/Kolkata (UTC plus 5:30). Conversions are ours and hold on every day of the year, because neither country changes its clocks.

Mentors teach only in English and adjust to each learner: shorter sentences, a slower pace and a word written in the chat when it helps. For a learner whose spoken English is still growing, the screen does a lot of the work, because code reads the same in every language. Families in the capital can read more on our page about English-medium coding classes in Lima, and learners in the south on coding classes in Arequipa.