Polymorphism through functions in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function that prints the length of any input.

Python

def print_length([1]):
    print(len(item))

print_length("hello")

Drag options to blanks, or click blank then click option'

Avalue

Blength

Citem

Dobj

Attempts:

3 left

💡 Hint

Common Mistakes

Using a parameter name different from the variable inside the function causes a NameError.

The function parameter should be named item because the print statement uses item to get the length.

2fill in blank

medium

Complete the code to call the function with a list argument.

Python

def print_length(item):
    print(len(item))

print_length([1])

Drag options to blanks, or click blank then click option'

A[1, 2, 3]

B5

C"hello"

Dlen

Attempts:

3 left

💡 Hint

Common Mistakes

Passing an integer like 5 causes a TypeError because integers have no length.

The function expects an object with length. A list like [1, 2, 3] works well.

3fill in blank

hard

Fix the error in the function to handle any input and print its length.

Python

def print_length(item):
    print([1](item))

print_length(12345)

Drag options to blanks, or click blank then click option'

Acount

Blen

Csize

Dlength

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined functions like length or size causes NameError.

The built-in function len() returns the length of an object. Using len(item) is correct.

4fill in blank

hard

Fill both blanks to create a function that works with strings and lists, printing their lengths.

Python

def print_length([1]):
    print(len([2]))

print_length("test")
print_length([1, 2, 3])

Drag options to blanks, or click blank then click option'

Adata

Citem

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names causes NameError.

The parameter and the variable inside len() must be the same. Here, both are data.

5fill in blank

hard

Fill all three blanks to create a function that prints the length of the uppercase version of a string argument.

Python

def print_upper_length([1]):
    upper_str = [2].upper()
    print(len([3]))

print_upper_length("hello")

Drag options to blanks, or click blank then click option'

Atext

Cupper_str

Dtext.upper()

Attempts:

3 left

💡 Hint

Common Mistakes

Using text.upper() directly in print causes error because it's not stored.

Mismatching variable names causes NameError.

The parameter is text. We call text.upper() and store it in upper_str. Then print length of upper_str.

Practice

1.

What does polymorphism through functions mean in Python?

easy

A. Functions cannot be reused with different inputs

B. Multiple functions have the same name but different parameters

C. Functions can only accept one specific data type

D. A single function works with different data types

Solution

1. Step 1: Understand polymorphism concept

   Polymorphism means one function can handle different types of inputs.

2. Step 2: Relate to function behavior

   In Python, a single function can accept various data types and behave accordingly.

3. Final Answer:

   A single function works with different data types -> Option D

4. Quick Check:

   Polymorphism = single function, many types [OK]

Hint: Think: one function, many input types [OK]

Common Mistakes:

• Confusing polymorphism with function overloading
• Believing functions accept only one data type
• Mixing polymorphism with inheritance

2.

Which of the following is the correct way to check a variable's type inside a function for polymorphism?

def process(value):
    # What to use here?
    pass

easy

A. if type(value) == int:

B. if value is int:

C. if isinstance(value, int):

D. if value == int:

Solution

1. Step 1: Recall Python type checking methods

   Using isinstance() is the recommended way to check type in Python.

2. Step 2: Compare options

   if isinstance(value, int): uses isinstance(value, int), which correctly checks if value is an int or subclass.

3. Final Answer:

   if isinstance(value, int): -> Option C

4. Quick Check:

   Use isinstance() for type checks [OK]

Hint: Use isinstance() to check types safely [OK]

Common Mistakes:

• Using 'type() == int' which fails with subclasses
• Using 'is' or '==' incorrectly for type comparison
• Not checking type at all

3.

What is the output of this code?

def describe(value):
    if isinstance(value, int):
        return f"Integer: {value}"
    elif isinstance(value, str):
        return f"String: {value}"
    else:
        return "Unknown type"

print(describe(10))
print(describe('hello'))
print(describe(3.14))

medium

A. Integer: 10\nString: hello\nUnknown type

B. Integer: 10\nString: hello\nFloat: 3.14

C. Unknown type\nUnknown type\nUnknown type

D. Integer: 10\nUnknown type\nUnknown type

Solution

1. Step 1: Check input 10

   10 is int, so returns 'Integer: 10'.

2. Step 2: Check input 'hello'

   'hello' is str, so returns 'String: hello'.

3. Step 3: Check input 3.14

   3.14 is float, not int or str, so returns 'Unknown type'.

4. Final Answer:

   Integer: 10 String: hello Unknown type -> Option A

5. Quick Check:

   Type checks match outputs [OK]

Hint: Match isinstance checks to output lines [OK]

Common Mistakes:

• Assuming float is handled like int or str
• Ignoring else case output
• Mixing output order

4.

Find the error in this polymorphic function and fix it:

def process(value):
    if isinstance(value, int):
        return value * 2
    elif isinstance(value, str):
        return value + value
    else:
        return value / 2

print(process('abc'))
print(process([1, 2, 3]))

medium

A. No error; code runs fine

B. Error: Cannot divide list by 2; fix by handling list separately

C. Error: Missing return statement for int type

D. Error: Cannot multiply string by 2; fix by converting to int

Solution

1. Step 1: Analyze input 'abc'

   String input returns 'abcabc' by concatenation, no error.

2. Step 2: Analyze input [1, 2, 3]

   List input goes to else: value / 2, but dividing list by 2 causes TypeError.

3. Step 3: Fix the error

   Need to add a check for list type or avoid dividing list by 2.

4. Final Answer:

   Error: Cannot divide list by 2; fix by handling list separately -> Option B

5. Quick Check:

   List / 2 causes error [OK]

Hint: Check operations valid for each type [OK]

Common Mistakes:

• Assuming all types support division
• Not testing with different input types
• Ignoring TypeError exceptions

5.

Write a polymorphic function combine that accepts either two strings or two lists and returns their concatenation. What is the output of this code?

def combine(a, b):
    if isinstance(a, str) and isinstance(b, str):
        return a + b
    elif isinstance(a, list) and isinstance(b, list):
        return a + b
    else:
        return None

print(combine('Hi, ', 'there!'))
print(combine([1, 2], [3, 4]))
print(combine('Hello', [1, 2]))

hard

A. 'Hi, there!'\n[1, 2, 3, 4]\nNone

B. 'Hi, there!'\n[1, 2]\n[3, 4]

C. None\nNone\nNone

D. 'Hi, there!'\nNone\nNone

Solution

1. Step 1: Check first call combine('Hi, ', 'there!')

   Both are strings, so returns concatenation 'Hi, there!'.

2. Step 2: Check second call combine([1, 2], [3, 4])

   Both are lists, so returns concatenated list [1, 2, 3, 4].

3. Step 3: Check third call combine('Hello', [1, 2])

   Types differ, so returns None.

4. Final Answer:

   'Hi, there!' [1, 2, 3, 4] None -> Option A

5. Quick Check:

   Type checks control output [OK]

Hint: Check types of both inputs before combining [OK]

Common Mistakes:

• Not checking both inputs' types
• Trying to combine different types directly
• Returning wrong default for mismatched types