String validation checks in Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of string isalnum() method

What is the output of this Python code snippet?

Python

s = "Hello123"
print(s.isalnum())

A True

B False

C SyntaxError

D TypeError

💡 Hint

isalnum() returns True if all characters are letters or digits and string is not empty.

The string "Hello123" contains only letters and digits, so isalnum() returns True.

❓ Predict Output

intermediate

Output of string isdigit() with spaces

What will this code print?

Python

s = "123 456"
print(s.isdigit())

A False

B True

C SyntaxError

D TypeError

💡 Hint

Spaces are not digits.

The string contains a space character, which is not a digit, so isdigit() returns False.

❓ Predict Output

advanced

Result of islower() on mixed case string

What does this code output?

Python

s = "helloWorld"
print(s.islower())

A True

B SyntaxError

C TypeError

D False

💡 Hint

islower() returns True only if all letters are lowercase and there is at least one letter.

The string "helloWorld" has uppercase 'W', so islower() returns False.

❓ Predict Output

advanced

Output of isspace() with newline character

What will this code print?

Python

s = "\n"
print(s.isspace())

A False

B True

C SyntaxError

D TypeError

💡 Hint

isspace() returns True if all characters are whitespace characters.

The newline character is considered whitespace, so isspace() returns True.

❓ Predict Output

expert

Output of complex string validation expression

What is the output of this code?

Python

s = "Python3"
result = s.isalpha() or s.isalnum() and not s.isdigit()
print(result)

A False

B SyntaxError

C True

D TypeError

💡 Hint

Remember operator precedence: 'and' before 'or'.

Expression evaluates as s.isalpha() or (s.isalnum() and not s.isdigit()). s.isalpha() is False because of '3'. s.isalnum() is True, s.isdigit() is False, so overall True.