Type checking using type() in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of type() with mixed types

What is the output of this Python code?

Python

values = [42, 3.14, 'hello', [1, 2, 3]]
result = [type(v).__name__ for v in values]
print(result)

A ['int', 'int', 'str', 'list']

B ['int', 'float', 'str', 'list']

C ['int', 'float', 'string', 'list']

D ['int', 'float', 'str', 'tuple']

💡 Hint

Use type() and __name__ attribute to get the type names as strings.

The list contains an int, a float, a string, and a list. type() returns the exact type, and __name__ gives the type name as a string. So the output is ['int', 'float', 'str', 'list'].

❓ Predict Output

intermediate

Type checking with type() and condition

What will be printed by this code?

Python

x = 10
if type(x) == int:
    print('Integer')
else:
    print('Not integer')

A Integer

B Not integer

C TypeError

D SyntaxError

💡 Hint

Check if x is exactly an int using type().

x is assigned 10, which is an int. The condition type(x) == int is True, so it prints 'Integer'.

❓ Predict Output

advanced

Output of nested type() checks

What is the output of this code snippet?

Python

def check_type(val):
    if type(val) == list:
        return 'List of length ' + str(len(val))
    elif type(val) == dict:
        return 'Dict with keys ' + ','.join(val.keys())
    else:
        return 'Other type'

print(check_type({'a':1, 'b':2}))

A Dict with keys ['a', 'b']

B TypeError

C Other type

D Dict with keys a,b

💡 Hint

Check how keys() returns a view and how join expects strings.

val.keys() returns dict_keys(['a', 'b']), which can be joined by ',' to form 'a,b'. So the returned string is 'Dict with keys a,b'.

❓ Predict Output

advanced

Type checking with inheritance and type()

What will this code print?

Python

class Animal:
    pass

class Dog(Animal):
    pass

pet = Dog()
print(type(pet) == Animal)

A False

B True

C TypeError

D SyntaxError

💡 Hint

type() checks exact type, not inheritance.

pet is an instance of Dog, so type(pet) is Dog, not Animal. Therefore, type(pet) == Animal is False.

🧠 Conceptual

expert

Understanding type() vs isinstance()

Which statement is true about type() and isinstance() in Python?

A Both type() and isinstance() behave exactly the same for all objects.

B type() returns True if an object is an instance of a class or its subclasses, isinstance() returns exact type only.

C type() returns the exact type of an object, while isinstance() returns True for an object and its subclasses.

D type() can check multiple types at once, isinstance() cannot.

💡 Hint

Think about inheritance and how these functions treat subclasses.

type() returns the exact type of an object. isinstance() returns True if the object is an instance of the class or any subclass, making it more flexible for inheritance checks.

Practice

1. What does the type() function do in Python?

easy

A. It tells you the kind of data stored in a variable.

B. It changes the data type of a variable.

C. It prints the value of a variable.

D. It deletes a variable from memory.

Solution

1. Step 1: Understand the purpose of type()

   The type() function returns the data type of the given variable or value.

2. Step 2: Compare options with the function's purpose

   Only It tells you the kind of data stored in a variable. correctly states that type() tells the kind of data stored in a variable.

3. Final Answer:

   It tells you the kind of data stored in a variable. -> Option A

4. Quick Check:

   type() returns data type [OK]

Hint: Remember: type() shows data kind, not value or change [OK]

Common Mistakes:

• Thinking type() changes the variable's type
• Confusing type() with print()
• Assuming type() deletes variables

2. Which of the following is the correct syntax to check the type of variable x?

easy

A. type x

B. type[x]

C. type(x)

D. check_type(x)

Solution

1. Step 1: Recall the syntax of the type() function

   The correct syntax uses parentheses around the variable: type(x).

2. Step 2: Evaluate each option

   type(x) matches the correct syntax. Options A and B use wrong brackets or missing parentheses. check_type(x) is not a valid Python function.

3. Final Answer:

   type(x) -> Option C

4. Quick Check:

   Use parentheses with type() [OK]

Hint: Use parentheses with functions like type() [OK]

Common Mistakes:

• Using square brackets instead of parentheses
• Omitting parentheses
• Using non-existent functions like check_type()

3. What will be the output of this code?

value = 3.14
print(type(value))

medium

A. <class 'float'>

B. <class 'int'>

C. <class 'str'>

D. Error

Solution

1. Step 1: Identify the data type of value

   The variable value is assigned 3.14, which is a decimal number, so its type is float.

2. Step 2: Understand what print(type(value)) outputs

   The type() function returns <class 'float'> for a float value, which is printed.

3. Final Answer:

   <class 'float'> -> Option A

4. Quick Check:

   3.14 is float type [OK]

Hint: Decimals are float type in Python [OK]

Common Mistakes:

• Confusing float with int
• Expecting string output
• Thinking it causes an error

4. Find the error in this code snippet:

my_var = 'hello'
if type(my_var) == str:
print('It is a string')

medium

A. Missing colon after if statement

B. Indentation error in print statement

C. Variable name is invalid

D. Incorrect use of type() function

Solution

1. Step 1: Check the if statement syntax

   The if statement has a colon and uses type() correctly, so no error there.

2. Step 2: Check indentation of the print statement

   In Python, the code inside if must be indented. Here, print is not indented, causing an indentation error.

3. Final Answer:

   Indentation error in print statement -> Option B

4. Quick Check:

   Indent inside if blocks [OK]

Hint: Indent code inside if statements [OK]

Common Mistakes:

• Forgetting to indent after if
• Misusing type() comparison
• Missing colon after if

5. You want to write a function that returns True if the input is an integer or a float, and False otherwise. Which code correctly uses type() to do this?

hard

A. def check_num(x):
return type(x) == int and float

B. def check_num(x):
return type(x) == int or float

C. def check_num(x):
return type(x) == 'int' or 'float'

D. def check_num(x):
return type(x) in [int, float]

Solution

1. Step 1: Understand the goal

   The function should return True if x is either int or float.

2. Step 2: Analyze each option's correctness

   def check_num(x): return type(x) == int or float uses or float incorrectly, always returning truthy. def check_num(x): return type(x) in [int, float] uses in to check membership in a list of types, which is concise and correct. def check_num(x): return type(x) == 'int' or 'float' compares type to strings, which is wrong. def check_num(x): return type(x) == int and float uses and incorrectly, only detecting ints.

3. Final Answer:

   def check_num(x): return type(x) in [int, float] -> Option D

4. Quick Check:

   Use in to check multiple types [OK]

Hint: Use 'type(x) in [int, float]' for multiple types [OK]

Common Mistakes:

• Comparing type to string names
• Using 'and' instead of 'or' or 'in'
• Using incomplete logic like '== int or float'