Data types

Python · Unit 1: First steps

Every value has a type: int for whole numbers, float for decimals, str for text and bool for true or false.

type() tells you what type something is.

print(type(42))
print(type(3.5))
print(type("hello"))
print(type(True))

Prints

<class 'int'>
<class 'float'>
<class 'str'>
<class 'bool'>

A number inside quotes is text: "42" is str, not int.

And between texts, + doesn't add: it glues them.

print(type("42"))
print("Hello" + "world")

Prints

<class 'str'>
Helloworld

To change type use int(), float() or str().

int("5") turns the text into the number 5, and str(5) does the opposite.

print(int("5") + 5)
print(str(5) + "5")
print(float("2.5"))

Prints

10
55
2.5

Text plus a number is an error (TypeError): Python doesn't know if you want to add or to glue.

Convert the number with str(), or use commas in print().

price = 50
print("Costs " + str(price))
print("Costs", price)

Prints

Costs 50
Costs 50

Exercises in this lesson

You do them in the app, which checks them on the spot and explains why.

1. Multiple choice
What type is True?
2. Complete the code
Fill in to find out what type 3.0 is.
```
print(___(3.0))
```
3. Predict the output
What does this code print?
```
print(type(7 / 2))
```
4. Put the lines in order
Order the lines to print the type of a price.
5. Multiple choice
Which of these values is text (str)?
6. Predict the output
What does this code print?
```
print("3" + "4")
```
7. Complete the code
Fill in to turn the text into a number and add 1 to it.
```
age = ___("17")
print(age + 1)
```
8. Find the bug
This program should print double 20. Which line has the error?
```
text = "20"
double = text * 2
print(double)
```
9. Multiple choice
What happens with "5" + 5?
10. Find the bug
This program should print "Emma is 17 years old". Which line has the error?
```
age = 17
phrase = "Emma is " + age
print(phrase, "years old")
```

11. Predict the output

What does this code print?

a = "7"
b = 3
print(int(a) + b)
print(a + str(b))

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