String Basics and Memory Representation in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of String Slicing and Concatenation

What is the output of the following Python code?

DSA Python

s = "hello"
result = s[1:4] + s[0]
print(result)

A "helh"

B "ello"

C "elloh"

D "ellh"

💡 Hint

Remember string slicing s[start:end] includes start but excludes end.

The slice s[1:4] takes characters from index 1 to 3, which are 'e', 'l', 'l'. Adding s[0] which is 'h' results in 'ellh'.

🧠 Conceptual

intermediate

Understanding String Immutability

Which statement best describes why strings in Python are immutable?

A Because changing a string would require creating a new string object in memory.

B Because strings are stored in a fixed-size memory block that cannot be changed.

C Because strings are stored as linked lists of characters that cannot be altered.

D Because strings are mutable but Python hides this from the user.

💡 Hint

Think about what happens when you try to change a character in a string.

Strings are immutable because any change creates a new string object; the original string's memory cannot be altered.

❓ Predict Output

advanced

Output of String Interning Behavior

What is the output of this code snippet?

DSA Python

a = "python"
b = "python"
c = ''.join(['p', 'y', 't', 'h', 'o', 'n'])
print(a is b)
print(a is c)

A True\nTrue

B True\nFalse

C False\nFalse

D False\nTrue

💡 Hint

The 'is' operator checks if two variables point to the same object in memory.

String literals like 'python' are interned and share the same memory, so a is b is True. But c is created dynamically, so a is c is False.

🔧 Debug

advanced

Identify the Error in String Modification Attempt

What error does the following code raise?

DSA Python

s = "immutable"
s[0] = 'I'

A TypeError: 'str' object does not support item assignment

B IndexError: string index out of range

C SyntaxError: invalid syntax

D AttributeError: 'str' object has no attribute '0'

💡 Hint

Strings cannot be changed by assigning to an index.

Strings are immutable in Python, so trying to assign a character to an index raises a TypeError.

🚀 Application

expert

Memory Size Comparison of Strings

Given two strings s1 = 'abc' and s2 = 'a' + 'b' + 'c', which statement about their memory usage is correct?

A s1 uses more memory because it is a literal, s2 uses less because it is concatenated.

B s1 and s2 are the same object only if explicitly interned using sys.intern().

C s1 and s2 are different objects with separate memory allocations.

D s1 and s2 always share the same memory location due to interning.

💡 Hint

Consider how Python handles string literals vs runtime concatenation.

String literals like s1 may be interned, but s2 is created at runtime by concatenation, so they are different objects in memory.