Lesson 31

Module 2 summary: Decisions

After this lesson: You'll go over the whole module and solve tasks that combine comparisons, ifs, and/or and the helpers.

Video

The video for this lesson is coming soon.

Explanation

Well done, this is the end of the second module! 🎉 Your programs can already decide. In this lesson we'll go over everything, and at the end we'll build a real quiz show - with questions, points and a final score!

What you already know

Lessons	Topic
19, 20	comparisons `> < >= <= == !=`, the values True and False
21, 22, 23	`if`, `else` and `elif` - one, two or many roads
24	divisibility: `n % k == 0`
25	joining conditions: `and`, `or`, `not`
26	an if inside an if - a question behind a gate
27	comparing text
28, 29	guards and catching mistakes
30	a plan for a contest task

1. Questions: comparisons and True / False

A comparison is a question, and the answer is True or False. One = puts into a box, two == ask. >= and <= count the limit too.

Recap: the scale

Click the arrow - we'll put every comparison on the scale.

Code

1age = 12
2print(age >= 12)
3print(age > 12)
4print(age == 12)

Screen

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2. Roads: if, else, elif

if - a road only for True, else - for everything else, elif - another sign with a condition.
Python checks from the top and picks the first true condition.
The lines of each road are indented by 4 spaces, and every header ends with a colon.

Recap: the fork

🏃1points = 77

if points >= 90

3print("Gold 🥇")

🥇

elif points >= 70

5print("Silver 🥈")

🥈

elif points >= 50

7print("Bronze 🥉")

🥉

elsein every other case

9print("Try again")

💪

Click the arrow - I'll walk the program's path, line by line.

Code

1points = 77
2if points >= 90:
3    print("Gold 🥇")
4elif points >= 70:
5    print("Silver 🥈")
6elif points >= 50:
7    print("Bronze 🥉")
8else:
9    print("Try again")

Screen

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3. Joining conditions

and - all the parts true (switches one after another), or - at least one (side by side), not - the other way round. Each side of and / or must be a whole question.

Recap: the circuit

🔋 ─ ⏻ ─ 💡

Click the arrow - you'll see the condition as a circuit with switches and a bulb.

Code

1n = 14
2if n % 2 == 0 and n > 10:
3    print("A big even number")
4else:
5    print("Something else")

Screen

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4. Guards and tests

Check first, then calculate: a guard (an if) stands before a division and catches wrong data.
Test the limits and every road of the program.

Bajtek's quiz show 🎬

Click Next - the grand finale: a program that puts the whole module together.

Bajtek

🎤❓❓❓➡️🏆

Lights, camera, action!

Bajtek hosts a quiz show 🎤. There are three questions. For every right answer the player gets a point, and at the end - a score.

Step 1 / 3

Play the quiz show 🎤

Three questions: what is 3 + 4? How many legs does a spider 🕷️ have? What is 12 // 4? Type three numbers, Enter ⏎ after each - and see your prize!

📦 points

⭐…

Code

1points = 0
2ans_str = input()
3ans = int(ans_str)
4if ans == 7:
5    points = points + 1
6ans_str = input()
7ans = int(ans_str)
8if ans == 8:
9    points = points + 1
10ans_str = input()
11ans = int(ans_str)
12if ans == 3:
13    points = points + 1
14print("Points:", points)
15if points == 3:
16    print("🏆 Champion!")
17elif points == 2:
18    print("🥈 Great!")
19elif points == 1:
20    print("👍 Not bad!")
21else:
22    print("💪 Try again!")

Screen

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What will this program print?

x = 6
if x % 3 == 0 and x > 5:
    print("A")
elif x > 5:
    print("B")
else:
    print("C")

What will this program print?

a = 3
b = 8
wieksza = a
if b > wieksza:
    wieksza = b
print(wieksza)

Which condition is true for Saturday (6) and Sunday (7) - and only for them?

Which if checks whether we can divide by b?

Remember

A comparison gives True or False, and == asks whether equal.
if / elif / else: Python picks the first true condition; a colon and indentation of 4 spaces.
and - all of them, or - at least one, not - the other way round.
n % k == 0 - divisibility; a tournament of ifs finds the biggest number.
The guard first, then the calculation. Test the limits and every road.

What's next?

In the next module programs will learn to repeat - the while and for loops. Then the quiz show can have not three but a hundred questions! 🔁

That's all of Module 2! Now the tasks - each one combines a few topics. Good luck!

Tasks from the video

We solve them together in the video - pause it and try first on your own.

1More, less, equal 2A big even number 3The quiz show 4A 3 for 2 deal 5The mark in words 6A dog's age 7Falling digits 8Closer to a hundred

Practice tasks

Try to solve them without the video. Stuck? Every task has hints and an editorial.

9A speeding ticket 10A leap year in one line 11No round numbers 12How many the same?