ReactCHALLENGES

1. Indexing

A string is text between quotes, like "Python". Each character has an index: a position counted from 0.

You read a single character with subscript syntax:

  • text — any string: for example "Python", or a variable that holds a string.
  • index — an integer (a whole number). 0 is the first character, 1 the second, and so on.
  • The result is a new string containing exactly one character.

A negative index counts from the end of the string: -1 is the last character, -2 the one before it.

Indexing works the same on a variable:

Only positions that exist are valid. "Python" has six characters, so its valid indexes are 0 to 5 and -1 to -6. Any other index raises an IndexError, an error that says the index is out of range, and the program stops:

#01

Read index 0

Index 0 is the first character of a string. Print the character at index 0 of "Python".

Print exactly:

Create a free account to save your progress and unlock chapter 2.

#02

Read a positive index

Index 1 is the second character, index 2 the third, and so on. Print the character at index 3 of "Python".

Print exactly:

Create a free account to save your progress and unlock chapter 2.

#03

Count from the end

A negative index counts from the end: -1 is the last character and -2 is the one before it. Print the character at index -2 of "Python".

Print exactly:

Create a free account to save your progress and unlock chapter 2.

#04

Both ends

Index 0 is the first character and index -1 is the last one. Print the first character of "Python", then its last character.

Print exactly:

Create a free account to save your progress and unlock chapter 2.

#05

Index a variable

Indexing works the same on a variable that holds a string. Create a variable named word with the value "Python", then print the character at index 1 using word.

Print exactly:

Create a free account to save your progress and unlock chapter 2.

#06

Trigger an IndexError

"Python" has 6 characters, so its valid indexes are 0 to 5 (and -1 to -6). Index 6 is out of range: reading it raises IndexError and the program stops.

Create a variable named word with the value "Python" and print word[6]. Running it must stop with:

Create a free account to save your progress and unlock chapter 2.