How variable type changes at runtime in Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to assign an integer value to the variable.

Python

x = [1]

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

A10

B3.14

C"hello"

DTrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around numbers makes them strings.

Using decimal points makes the number a float.

The variable x is assigned the integer value 10.

2fill in blank

medium

Complete the code to change the variable to a string value.

Python

x = [1]

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

A100

B"world"

CFalse

D3.5

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around text.

Using numbers without quotes when a string is needed.

The variable x is now assigned the string value "world".

3fill in blank

hard

Fix the error in the code to assign a float value to the variable.

Python

x = [1]

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

A3.14

B3,14

C"3.14"

Dpi

Attempts:

3 left

💡 Hint

Common Mistakes

Using commas instead of dots for decimals.

Putting numbers in quotes makes them strings.

The variable x is assigned the float value 3.14 without quotes or commas.

4fill in blank

hard

Fill both blanks to create a variable that changes from integer to boolean.

Python

x = [1]
x = [2]

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

A5

BTrue

CFalse

D"5"

Attempts:

3 left

💡 Hint

Common Mistakes

Using quotes around True or False makes them strings.

Assigning a string instead of an integer first.

First, x is assigned the integer 5. Then it changes to the boolean value True.

5fill in blank

hard

Fill all three blanks to show a variable changing from string to float to integer.

Python

x = [1]
x = [2]
x = [3]

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

A"7.5"

B7.5

C7

D7.0

Attempts:

3 left

💡 Hint

Common Mistakes

Keeping quotes when changing to float or integer.

Using 7.0 instead of 7 for the integer value.

The variable x starts as a string "7.5", then changes to a float 7.5, and finally to an integer 7.

Practice

1. What happens to the type of a Python variable when you assign a new value of a different type to it?

easy

A. The variable's type changes to the new value's type automatically.

B. The variable keeps its original type regardless of the new value.

C. Python raises an error if the new value's type is different.

D. The variable becomes a list containing both old and new types.

Solution

1. Step 1: Understand Python variable typing

   Python variables are dynamically typed, meaning their type depends on the current value assigned.

2. Step 2: Assigning a new value changes the type

   When you assign a new value of a different type, the variable's type updates to match the new value automatically.

3. Final Answer:

   The variable's type changes to the new value's type automatically. -> Option A

4. Quick Check:

   Python variables are dynamic = A [OK]

Hint: Remember: Python variables follow the value's type, not fixed type. [OK]

Common Mistakes:

• Thinking variables have fixed types like in some other languages.
• Assuming Python throws an error on type change.
• Believing variable types combine old and new types.

2. Which of the following is the correct way to assign a new value to a variable in Python so its type changes?

easy

A. x = 10

B. x := 10

C. int x = 10

D. var x = 10

Solution

1. Step 1: Identify Python assignment syntax

   Python uses the single equals sign (=) to assign values to variables.

2. Step 2: Check each option

   x = 10 uses correct syntax. x := 10 uses walrus operator which is for expressions, not simple assignment. int x = 10 and var x = 10 are invalid in Python.

3. Final Answer:

   x = 10 -> Option A

4. Quick Check:

   Assignment uses = in Python = A [OK]

Hint: Use single '=' for assignment in Python, not ':=' or types. [OK]

Common Mistakes:

• Confusing ':=' walrus operator with assignment.
• Using typed declarations like other languages.
• Trying to declare variable types explicitly.

3. What will be the output of this code?

var = 5
print(type(var))
var = 'hello'
print(type(var))

medium

A. \n

B. \n

C. \n

D. Error

Solution

1. Step 1: Check initial assignment and type

   var is first assigned 5, an integer, so type(var) is <class 'int'>.

2. Step 2: Reassign and check new type

   var is then assigned 'hello', a string, so type(var) is <class 'str'>.

3. Final Answer:

   <class 'int'>\n<class 'str'> -> Option C

4. Quick Check:

   Type changes with value = C [OK]

Hint: Track variable type after each assignment line by line. [OK]

Common Mistakes:

• Assuming type stays the same after reassignment.
• Confusing output order of print statements.
• Expecting a runtime error on type change.

4. Find the error in this code snippet:

value = 10
value = value + '5'
print(value)

medium

A. NameError because 'value' is undefined

B. SyntaxError due to invalid assignment

C. No error, output is 15

D. TypeError because int and str cannot be added

Solution

1. Step 1: Analyze the operation between int and str

   value is an int (10), then tries to add a string ('5'), which is not allowed.

2. Step 2: Identify the error type

   Python raises a TypeError when adding incompatible types like int and str.

3. Final Answer:

   TypeError because int and str cannot be added -> Option D

4. Quick Check:

   Adding int + str causes TypeError = D [OK]

Hint: Check types before adding; int + str causes error. [OK]

Common Mistakes:

• Thinking Python auto-converts types in addition.
• Expecting output '15' as string concatenation.
• Confusing SyntaxError with TypeError.

5. Given the code below, what will be the final type of data?

data = 100
if isinstance(data, int):
    data = str(data)
else:
    data = [data]

hard

A. int

B. str

C. list

D. bool

Solution

1. Step 1: Check initial type of data

   data starts as 100, which is an int.

2. Step 2: Evaluate the if condition

   Since data is int, the if block runs, converting data to str('100').

3. Final Answer:

   str -> Option B

4. Quick Check:

   int converted to str by condition = B [OK]

Hint: If int, convert to str; else make list. [OK]

Common Mistakes:

• Ignoring the if condition and assuming list.
• Thinking data remains int after reassignment.
• Confusing str and bool types.