Type checking using type() in Python - Step-by-Step Execution

Concept Flow - Type checking using type()

Start

↓

Have a variable

↓

Call type(variable)

↓

Get type result

↓

Compare or print type

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Use type info as needed

↓

End

This flow shows how Python checks the type of a variable using the type() function and then uses that information.

Execution Sample

Python

x = 10
print(type(x))
y = 'hello'
print(type(y))

This code checks and prints the types of two variables: an integer and a string.

Execution Table

Step	Action	Variable	type(variable)	Output
1	Assign 10 to x	x=10	int
2	Call type(x)	x=10	int	<class 'int'>
3	Print type(x)	x=10	int	<class 'int'>
4	Assign 'hello' to y	y='hello'	str
5	Call type(y)	y='hello'	str	<class 'str'>
6	Print type(y)	y='hello'	str	<class 'str'>

💡 All variables checked and their types printed.

Variable Tracker

Variable	Start	After Step 1	After Step 4	Final
x	undefined	10	10	10
y	undefined	undefined	'hello'	'hello'

Key Moments - 2 Insights

Why does type(x) return <class 'int'> instead of just 'int'?

type() returns the type object, which prints as <class 'int'>. This shows the variable's type clearly. See execution_table step 2.

Can type() tell the difference between strings and numbers?

Yes, type() returns different type objects like <class 'int'> for numbers and <class 'str'> for strings, as shown in steps 2 and 5.

Visual Quiz - 3 Questions

Look at the execution_table at step 5, what is the type of variable y?

A <class 'int'>

B <class 'str'>

C <class 'float'>

D <class 'list'>

💡 Hint

Check the 'type(variable)' column at step 5 in the execution_table.

At which step is the variable x assigned a value?

A Step 1

B Step 2

C Step 4

D Step 5

💡 Hint

Look at the 'Action' and 'Variable' columns in the execution_table for when x gets a value.

If we change x to 3.14, what would type(x) return?

A <class 'int'>

B <class 'str'>

C <class 'float'>

D <class 'bool'>

💡 Hint

Recall that 3.14 is a decimal number, which Python treats as float.

Concept Snapshot

type(variable) returns the type of the variable.
It shows the class like <class 'int'> or <class 'str'>.
Use it to check what kind of data a variable holds.
Useful for debugging or conditional checks.
Example: type(x) == int checks if x is an integer.

Full Transcript

This lesson shows how Python's type() function checks the type of a variable. We assign values to variables x and y, then call type() on them. The output shows <class 'int'> for x when it holds 10, and <class 'str'> for y when it holds 'hello'. This helps us understand what kind of data each variable contains. Beginners often wonder why the output shows <class 'int'> instead of just int; this is Python's way of showing the type object clearly. The execution table traces each step, showing variable assignments and type checks. The variable tracker shows how x and y change from undefined to their assigned values. Quizzes test understanding of variable types and when assignments happen. Remember, type() is a simple way to see what data type a variable has in Python.

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'