Type conversion (int, float, string) in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of mixed type conversions

What is the output of this Python code?

Python

a = '123'
b = 4.56
c = int(float(a)) + int(b)
print(c)

A TypeError

B 127.56

C 127

D 124

💡 Hint

Remember int() converts float to integer by dropping decimals.

The string '123' is converted to float 123.0, then to int 123. The float 4.56 is converted to int 4 by dropping decimals. Sum is 123 + 4 = 127.

❓ Predict Output

intermediate

String to int conversion with invalid input

What error does this code raise?

Python

x = '12.3'
y = int(x)
print(y)

A ValueError

B TypeError

C SyntaxError

D No error, prints 12

💡 Hint

int() cannot convert strings with decimal points directly.

Trying to convert '12.3' directly to int causes ValueError because it's not a valid integer string.

❓ Predict Output

advanced

Output of chained conversions and operations

What is the output of this code?

Python

val = 7.89
result = str(int(val)) + str(round(val))
print(result)

A "7.89"

B "78"

C "77"

D "79"

💡 Hint

int(val) drops decimals, round(val) rounds normally.

int(7.89) is 7, round(7.89) is 8, concatenated as strings gives '78'.

❓ Predict Output

advanced

Result of converting boolean to int and string

What is the output of this code?

Python

flag = True
num = int(flag)
text = str(flag)
print(num, text)

A 0 False

B True 1

C TypeError

D 1 True

💡 Hint

Boolean True converts to 1 as int, and 'True' as string.

int(True) is 1, str(True) is 'True'. So print outputs: 1 True

🧠 Conceptual

expert

Understanding type conversion behavior

Which option correctly describes the output of this code snippet?

Python

data = ['1', '2.5', '3']
converted = [int(float(x)) for x in data]
print(converted)

A [1, 2, 3]

B [1, 2.5, 3]

C [1, 3, 3]

D ValueError

💡 Hint

float(x) converts string to float, int() drops decimals.

Each string is converted to float then to int, so '2.5' becomes 2, resulting list is [1, 2, 3].

Practice

1. What does the Python function int() do when applied to a string like '123'?

easy

A. Converts the string to the integer 123

B. Converts the string to the float 123.0

C. Leaves the string unchanged

D. Causes a syntax error

Solution

1. Step 1: Understand int() function behavior

   The int() function converts a string containing digits into an integer number.

2. Step 2: Apply int() to '123'

   Applying int('123') converts the string to the integer 123.

3. Final Answer:

   Converts the string to the integer 123 -> Option A

4. Quick Check:

   int('123') = 123 [OK]

Hint: int() turns digit strings into whole numbers [OK]

Common Mistakes:

• Thinking int() converts to float
• Expecting string unchanged
• Confusing with syntax error

2. Which of the following is the correct syntax to convert the float number 3.14 to an integer in Python?

easy

A. int(3,14)

B. int '3.14'

C. int(3.14)

D. int(3.14.0)

Solution

1. Step 1: Recall correct function call syntax

   Functions in Python require parentheses around arguments, e.g., int(3.14).

2. Step 2: Check each option

   int(3.14) uses correct syntax. Others have syntax errors or invalid argument formats.

3. Final Answer:

   int(3.14) -> Option C

4. Quick Check:

   int(3.14) is valid syntax [OK]

Hint: Use parentheses with int() for conversion [OK]

Common Mistakes:

• Omitting parentheses
• Using commas instead of dots
• Adding extra dots in numbers

3. What is the output of this code?

value = '45.67'
result = float(value)
print(int(result))

medium

A. 46

B. 45

C. Error

D. 45.67

Solution

1. Step 1: Convert string to float

   float('45.67') converts the string to the float number 45.67.

2. Step 2: Convert float to int

   int(45.67) converts the float to integer by dropping the decimal part, resulting in 45.

3. Final Answer:

   45 -> Option B

4. Quick Check:

   int(float('45.67')) = 45 [OK]

Hint: int() drops decimals, does not round [OK]

Common Mistakes:

• Expecting rounding to 46
• Printing float instead of int
• Confusing string and number types

4. The code below causes an error. What is the fix?

num = 'abc'
converted = int(num)
print(converted)

medium

A. Use float() instead of int()

B. Add quotes around int

C. Remove the int() conversion

D. Change 'abc' to a string of digits like '123'

Solution

1. Step 1: Identify cause of error

   Trying to convert 'abc' to int causes a ValueError because 'abc' is not numeric.

2. Step 2: Fix by using numeric string

   Replacing 'abc' with a string of digits like '123' allows int() to convert successfully.

3. Final Answer:

   Change 'abc' to a string of digits like '123' -> Option D

4. Quick Check:

   int('123') works, int('abc') errors [OK]

Hint: int() needs numeric strings, not letters [OK]

Common Mistakes:

• Using float() on non-numeric string
• Removing conversion but expecting int
• Adding quotes around function name

5. You have a list of mixed strings representing numbers: ['10', '20.5', '30', '40.0']. How do you convert all to integers correctly in Python?

hard

A. Use [int(float(x)) for x in list]

B. Use [int(x) for x in list]

C. Use [float(int(x)) for x in list]

D. Use [str(int(x)) for x in list]

Solution

1. Step 1: Understand list contents

   The list has strings representing integers and floats, e.g., '20.5' and '40.0'.

2. Step 2: Convert strings to float first

   Direct int() on '20.5' causes error, so convert to float first: float('20.5') = 20.5.

3. Step 3: Convert float to int

   Then convert float to int with int(20.5) = 20, dropping decimals.

4. Final Answer:

   Use [int(float(x)) for x in list] -> Option A

5. Quick Check:

   int(float('20.5')) = 20 [OK]

Hint: Convert string to float, then to int for decimals [OK]

Common Mistakes:

• Trying int() directly on float strings
• Swapping int and float conversions
• Converting to string instead of int