Printing objects

Python · Unit 12: Classes and objects

Full plan
Python
10 exercises

If you print an object of yours, Python doesn't know what to show: you get something like <__main__.Pet object at 0x7f3a…>, its type and a memory number that changes every time.

If the class has a __str__ method that returns a string, print shows that string.

class Pet:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return "I'm " + self.name

luna = Pet("Luna")
print(luna)

Prints

I'm Luna

The rest of the explanation is in the lesson, which is part of the full plan.

Exercises in this lesson

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

1. Multiple choice
The Book class has no __str__. What comes out with print(book)?
2. Predict the output
What does this code print?
3. Complete the code
Complete it so it prints: 10 coins
4. Find the bug
This program should print 5 km. Which line has the error?
5. Complete the code
Complete it so it prints: Table 4
6. Predict the output
What does this code print?
7. Predict the output
What does this code print?
8. Multiple choice
If a class has __repr__ but no __str__, what does print show for one of its objects?
9. Find the bug
This program should print [Tile(4), Tile(9)]. Which line has the error?
10. Predict the output
What does this code print?

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