For Loops w/ Strings & Lists

Both strings and lists are indexable, so we can access individual items by indicating an index with square brackets.

Examples:

print('Hello'[1]) # Should output letter 'e' at index of 1

print(['Apple', 'Bananas', 'Kiwi', 'Strawberry'][2]) # Outputs Kiwi

Examples of indexing with a For Loop

Code

# Using a for loop on a string with index
# NOTE: programmers often use single letters when creating an iterating variable
# I like to use i as "index"

phrase = 'Hello, World!'
size = len(phrase)

for i in range(size):
    print('Current character at index', i, 'is:', phrase[i])

Output

Current character at index 0 is: H
Current character at index 1 is: e
Current character at index 2 is: l
Current character at index 3 is: l
Current character at index 4 is: o
Current character at index 5 is: ,
Current character at index 6 is:  
Current character at index 7 is: W
Current character at index 8 is: o
Current character at index 9 is: r
Current character at index 10 is: l
Current character at index 11 is: d
Current character at index 12 is: !

Code

# Using for loop on a list of fruits via index

fruits = ['Apple', 'Banana', 'Kiwi', 'Strawberry']

print('The fruits in my blender:')

for i in range(len(fruits)):
    print('    --', fruits[i])

Output

The fruits in my blender:
    -- Apple
    -- Banana
    -- Kiwi
    -- Strawberry

• recall that range() never includes the last value

• indexing in Python always starts at 0(zero).

• Therefore, a string of: Hello has its last character at index of 4, but has a length of 5

• Same idea applies to lists as well.

Accessing items in a String or a List without indexing

We can also just iterate through strings or lists by using a for loop without the need for the index values.

Code

# For loop on string

phrase = 'Hello, World!'

for character in phrase:
    print('Current Character:', character)

Example

Current Character: H
Current Character: e
Current Character: l
Current Character: l
Current Character: o
Current Character: ,
Current Character:  
Current Character: W
Current Character: o
Current Character: r
Current Character: l
Current Character: d
Current Character: !

Code

# For loop on list

fruits = ['Apple', 'Banana', 'Kiwi', 'Strawberry']

for fruit in fruits:
    print('Current fruit:', fruit)

Example

Current fruit: Apple
Current fruit: Banana
Current fruit: Kiwi
Current fruit: Strawberry