Type checking using type() in Python - Mini Project: Build & Apply

Type Checking Using type()

📖 Scenario: You are working on a program that needs to handle different types of data carefully. Sometimes, you need to check what type of data you have before doing something with it.

🎯 Goal: Build a simple Python program that creates different variables, checks their types using the type() function, and prints the results.

📋 What You'll Learn

Create variables of different types: integer, string, and list

Create a variable called data_type to store the type of a variable

Use type() to find the type of each variable

Print the type of each variable

💡 Why This Matters

🌍 Real World

Type checking helps programs handle data correctly, avoiding errors when working with different kinds of information.

💼 Career

Many programming jobs require understanding data types to write safe and bug-free code.

1

Create variables of different types

Create three variables: number with the value 10, text with the value 'hello', and items with the value [1, 2, 3].

Python

# Create variables number, text, and items with the given values
# Your code here

Hint

Use simple assignment to create each variable with the exact values.

2

Create a variable to hold the type

Create a variable called data_type and set it to None as a placeholder.

Python

number = 10
text = 'hello'
items = [1, 2, 3]

# Create a variable data_type and set it to None
# Your code here

Hint

This variable will store the type information later.

3

Use type() to find the type of each variable

Use the type() function to find the type of number, text, and items. Assign the type of number to data_type. Then create variables text_type and items_type to store the types of text and items respectively.

Python

number = 10
text = 'hello'
items = [1, 2, 3]
data_type = None

# Assign the type of number to data_type
# Create text_type and items_type to store types of text and items
# Your code here

Hint

Use type(variable) to get the type of each variable.

4

Print the types of the variables

Print the values of data_type, text_type, and items_type each on a separate line.

Python

number = 10
text = 'hello'
items = [1, 2, 3]
data_type = None
data_type = type(number)
text_type = type(text)
items_type = type(items)

# Print data_type, text_type, and items_type
# Your code here

Hint

Use three print() statements to show the types.

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'