Lesson 19
Comparisons: greater, less, equal
After this lesson: You'll ask Python a question about two numbers and get the answer True or False.
Video
The video for this lesson is coming soon.
Explanation
Welcome to module 2! 🎉 So far your programs always did the same thing - line by line, from top to bottom. Now we'll teach them to decide: one thing for a 10-year-old, another for a 15-year-old. But to decide, you first need to be able to ask a question. For example: is 7 greater than 5?
Who has more sweets? 🎬
Click Next and see how Python answers questions.
An argument about sweets
Ola has 7 sweets 🍬, and Kuba 5. Kuba says: "I have the same!". Ola: "Not true, I have more!". Bajtek takes a scale to check.
Six questions
Python knows six comparison signs. Each one is a different question:
| Sign | Question | Example | Answer |
|---|---|---|---|
> | greater? | 7 > 5 | True |
< | less? | 7 < 5 | False |
>= | greater or equal? | 5 >= 5 | True |
<= | less or equal? | 4 <= 3 | False |
== | equal? | 6 == 6 | True |
!= | different? | 6 != 6 | False |
The signs >=, <=, == and != are two characters written together, with no space. The equals sign always comes second: >=, not =>. The exclamation mark ! in != means "not": not equal.
Play with the scale ⚖️
Set two numbers with the buttons - and see which of the six questions are answered True.
Change a and b with the buttons - and watch which comparisons are true. Try setting two equal numbers!
The scale answers questions
We put every comparison on the scale: the bigger number weighs more, and the lamp shows True or False.
Click the arrow - we'll put every comparison on the scale.
1print(7 > 5)2print(3 > 8)3print(4 == 4)4print(6 != 6)5print(2 <= 9)
▍One sign = or two ==?
This is very important and easy to mix up:
| Code | What it does |
|---|---|
age = 12 | puts 12 into the box age 📦 |
age == 12 | asks: is there 12 in the box age? ❓ |
One = sign is putting in, two signs == are a question. We can compare variables too - Python first looks into the box, then compares what's inside.
Putting in and asking
Line 1 puts 12 into the box. Then three questions about what's inside.
Click the arrow - we'll put every comparison on the scale.
1age = 122print(age == 12)3print(age == 13)4print(age > 10)
▍A ride from 120 cm 🎬
Click Next - you'll see how >= works.
The sign by the ride
By the ride 🎢 there's a sign: entry from 120 cm. Bajtek has to measure the children and let in only those who may ride.
The limit on the scale
The same 12 twice - once with >, once with >=.
Click the arrow - we'll put every comparison on the scale.
1print(12 > 12)2print(12 >= 12)3print(11 <= 12)
▍Can you get on the ride? 🎢
Type your height in cm 📏 (e.g. 135) and press Enter ⏎. Try 120 too - the limit itself!
Click the arrow - we'll measure the height by the ruler.
1height_str = input()2height = int(height_str)3print("You can ride:", height >= 120)
▍First calculating, then the question
There can be calculations on both sides of a comparison. Python calculates first, and only then compares. 2 + 3 == 5 is: first 2 + 3 gives 5, then the question 5 == 5 - True.
Calculate and weigh
The results go on the scale already calculated.
Click the arrow - we'll put every comparison on the scale.
1ola_sweets = 4 + 32kuba_sweets = 2 * 33print(ola_sweets > kuba_sweets)4print(ola_sweets == kuba_sweets + 1)
▍Guess Bajtek's number 🔢
Bajtek is thinking of the number 7. Type a number from 1 to 10 🔢 and press Enter ⏎ - the program says whether you guessed it.
Click the arrow - we'll put every comparison on the scale.
1number_str = input()2number = int(number_str)3print("Got it:", number == 7)4print("Too small:", number < 7)5print("Too big:", number > 7)
▍What will this program print?
print(10 > 3)
What will this program print?
print(4 >= 4)
What will this program print?
x = 3print(x != 3)
Which line ASKS whether the box holds 5?
Remember
- A comparison is a question - Python answers True or False.
- Six signs:
><>=<===!=. >=and<=count the limit too:120 >= 120is True, but120 > 120is False.- One
=puts into a box, two==ask whether equal. - Calculating first, then comparing:
2 + 3 == 5is True.
Now it's your turn! In the tasks you'll read numbers and print Python's answer: True or False.
Tasks from the video
We solve them together in the video - pause it and try first on your own.
Practice tasks
Try to solve them without the video. Stuck? Every task has hints and an editorial.
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