String Traversal and Character Access in DSA Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does string traversal mean?

String traversal means going through each character in a string one by one, usually from the first character to the last.

beginner

How do you access the third character in a string named text in Python?

You use text[2] because counting starts at zero. So the first character is text[0], second is text[1], and third is text[2].

beginner

What happens if you try to access a character at an index that is outside the string length?

You get an error called IndexError because the position does not exist in the string.

intermediate

Why is zero-based indexing used in string traversal?

Zero-based indexing means counting starts at 0. It helps computers calculate positions easily and is a common standard in programming.

beginner

How can you loop through each character in a string s in Python?

You can use a for loop like this:<br>for char in s:<br> print(char)<br>This prints each character one by one.

What is the index of the first character in a string?

A Depends on the string length

B 1

C -1

D 0

In most programming languages including Python, string indexing starts at 0.

What will print('hello'[1]) output?

A l

B h

C e

D o

Index 1 is the second character, which is 'e' in 'hello'.

Which of these will cause an error?

A Accessing <code>string[0]</code> in a non-empty string

B Accessing <code>string[len(string)]</code>

C Looping through string with <code>for char in string</code>

D Using <code>string[-1]</code> to get last character

Index equal to string length is out of range and causes IndexError.

How do you get the last character of a string s in Python?

A <code>s[-1]</code>

B <code>s[len(s)]</code>

C <code>s[0]</code>

D <code>s[len(s)-2]</code>

Negative index -1 accesses the last character in Python strings.

What does this code do?<br>for i in range(len(s)):<br> print(s[i])

A Prints each character in string s one by one

B Prints the length of s

C Prints the string s reversed

D Causes an error

It loops over each index and prints the character at that index.

Explain how to access characters in a string and what happens if you use an invalid index.

Think about how counting starts and what happens if you go beyond the string length.

Describe two ways to traverse a string in Python and print each character.

One way uses characters directly, the other uses indexes.