Lesson 27

Comparing text

After this lesson: You'll check a password and a command, and put words in alphabetical order.

Video

The video for this lesson is coming soon.

Explanation

So far we compared numbers. But == works on text too! That way a program can check a password, the answer to a riddle or a command for a robot. Careful: Python compares text letter by letter - and it's very precise! 🔍

The club's secret password 🎬

Click Next - you'll see that every letter counts for Python.

Bajtek

🚪"smok"🐉

The dragon club

Bajtek starts a club 🐉. The password is smok (Polish for dragon). A program stands at the door: if password == "smok": - let them in.

Step 1 / 5

Letter by letter

Watch where the first difference is - that's what decides.

k o t ⇄ k o t

Click the arrow - we'll compare the texts letter by letter.

Code

1password = "Smok"
2print(password == "smok")
3print(password == "Smok")
4print(password != "smok")

Screen

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The door to the dragon club 🐉

Type the password 🔑 and press Enter ⏎. Try Smok with a capital letter too!

k o t ⇄ k o t

Click the arrow - we'll compare the texts letter by letter.

Code

1password = input()
2if password == "smok":
3    print("Welcome to the club! 🐉")
4else:
5    print("Wrong password 🔒")

Screen

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A trap: a number in quotes 🎬

Click Next - why doesn't Python agree that 5 is 5?

Bajtek

But it says 5!🤨

Code

ans = input()

print(ans == 5)

🖥️ Screen

False

Bajtek's riddle

Bajtek asks: "How many legs does a dog have... counting the tail? 🐕". The program reads the answer: ans = input(). Kuba types 5. The program checks ans == 5... and says it's wrong!

Step 1 / 3

Text or number?

Three comparisons of the same answer - only the first one gives False.

Code

1ans = "5"
2print(ans == 5)
3print(ans == "5")
4print(int(ans) == 5)

Screen

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A smaller text? The order of a dictionary

Text can also be compared with < and >. Python orders it like a dictionary: it compares the first letters, and when they're the same - the next ones. The first different letter decides: earlier in the alphabet = the "smaller" text.

Comparison	Result	Why
`"kot" < "pies"`	True	k comes before p
`"kot" < "koza"`	True	ko = ko, then t before z
`"Ala" < "Ola"`	True	A comes before O

Fun fact: for Python all capital letters come before small ones, so "Zebra" < "ala" is True! In tasks all the words are usually written the same way (e.g. in small letters).

Bajtek's dictionary

Each comparison: the letters go in turn until the first different one turns up.

k o t ⇄ k o t

Click the arrow - we'll compare the texts letter by letter.

Code

1print("kot" < "pies")
2print("kot" < "koza")
3print("Ala" < "Ola")
4print("Zebra" < "ala")

Screen

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Who comes first in the register? 📒

Type two names 🧒 with a capital letter, each on its own line (e.g. Ola and Kuba). Enter ⏎ after each.

k o t ⇄ k o t

Click the arrow - we'll compare the texts letter by letter.

Code

1first = input()
2second = input()
3if first < second:
4    print(first)
5else:
6    print(second)

Screen

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A remote for the robot 🎮

Type a command 🎮: lewo (left), prawo (right) or stop - and press Enter ⏎. And what happens with another word?

🤖1command = input()

if command == "lewo"

3print("⬅️ Turning left")

⬅️

elif command == "prawo"

5print("➡️ Turning right")

➡️

elif command == "stop"

7print("🛑 Standing still")

🛑

elsein every other case

9print("❓ I don't know that command")

❓

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

Code

1command = input()
2if command == "lewo":
3    print("⬅️ Turning left")
4elif command == "prawo":
5    print("➡️ Turning right")
6elif command == "stop":
7    print("🛑 Standing still")
8else:
9    print("❓ I don't know that command")

Screen

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Only == and != for answers

When you check a password, a command or an answer, use == and !=. The signs < and > are useful for putting words in alphabetical order.

What will this program print?

print("Kot" == "kot")

What will this program print?

print("abc" < "abd")

The input is 7. What does the condition ans == 7 give when ans = input()?

Remember

== and != work on text - they compare character by character.
A capital and a small letter are different characters, and a space is a character too.
input() gives text: compare with "5" or use int(ans) == 5.
< and > order text like a dictionary - the first different letter decides.

On to the tasks! This time you read words - no int().

Tasks from the video

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

1The password 2The same word?3A command for the robot 4First in the dictionary 5The season 6tak or TAK?7Alphabetically 8Beep beep

Practice tasks

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

9Traffic lights 10A day off 11First of three 12Different words