OOP – String Representation (__str__)
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. What does __str__ control?
2. When is __str__ called?
3. What must __str__ return?
4. What does print(obj) show without __str__?
5. Does __str__ change the object?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1def __str__(self): return 42 | AOutput: 3.14 | |
| 2def Str(self): | BOk: Returns a formatted string from __str__ | |
| 3def __str__(self): | CValid: Defines string representation of an object | |
| 4return f'Dog: {self.name}' | DOutput: [1, 2] | |
| 5str(3.14) | EError: __str__ must return a string | |
| 6str([1, 2]) | FError: Magic method must be __str__ |
C
Definitions
__str__(self)
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
class Dog:
def _______(self):
return 'Dog: ' + self.name
2.
class Dog:
def _______(self):
______ self.name
3.
class Dog:
def __str__(self):
return 'Dog: ' + ____.name
4.
dog = Dog('Rex')
_____(dog)
5.
class Point:
def _______(self):
return '(' + str(____.x) + ')'
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
class Dog:
B
def __str__(self):
C
print('Dog: ' + self.name)
Question 2
A
class Dog:
B
def __str__(self):
C
return 42
Question 3
A
class Dog:
B
def __str__():
C
return 'Dog'
Question 4
A
class Dog:
B
def _str_(self):
C
return 'Dog'
Question 5
A
class Dog:
B
def str(self):
C
return 'Dog'
Answer Key
OOP – String Representation (__str__)
Section A: Quick Questions
Q1
B — What print(object) displays
Q2
A — When you print() or str() the object
Q3
A — A string
Q4
B — Something like <ClassName object at 0x...>
Q5
A — No it just returns a string description
Section B: Match the Pairs
Q1
def __str__(self):
return 42 → Error: __str__ must return a string
Q2
def Str(self): → Error: Magic method must be __str__
Q3
def __str__(self): → Valid: Defines string representation of an object
Q4
return f'Dog: {self.name}' → Ok: Returns a formatted string from __str__
Q5
str(3.14) → Output: 3.14
Q6
str([1, 2]) → Output: [1, 2]
Section C: Definitions
Q1
__str__(self) — Returns a human-readable string used by print() and str().~~__repr__(self)Section D: Fill in the Blanks
Q1
class Dog:
def __str__(self):
return 'Dog: ' + self.nameQ2
class Dog:
def __str__(self):
return self.nameQ3
class Dog:
def __str__(self):
return 'Dog: ' + self.nameQ4
dog = Dog('Rex')
print(dog)Q5
class Point:
def __str__(self):
return '(' + str(self.x) + ')'Section E: Spot the Error
Q1
C — __str__ must RETURN a string, not print it
Q2
C — __str__ must return a string, not an integer
Q3
B — Missing self parameter
Q4
B — Need double underscores: __str__ not _str_
Q5
B — Must be __str__ with double underscores not just str