The general structure of a for loop is as follows:

for <temporary variable> in <collection>
    <action>

Let’s break down each of these components:

• A for keyword indicates the start of a for loop.
• A <temporary variable> that is used to represent the value of the element in the collection the loop is currently on.
• An in keyword separates the temporary variable from the collection used for variation.
• A <collection> to loop over.
• An <action> to do anything on each iteration of the loop.

The following for loop prints each brand in brands.

chocolate_brands = ["Ferrero", "Lotus", "Campco"]

for brand in chocolate_brands:
    print(brand)

# Ferrero
# Lotus
# Campco

Indentation

Notice that the print statement in the code example above is indented. Everything at the same level of indentation after the for loop declaration is included in the loop body and is run on every iteration of the loop.

If we ever forget to indent, we’ll get an IndentationError or unexpected behavior.

For loops Using Range

For example, if we wanted to print out a Hello World! message six times using a for loop, we would follow this structure:

for <temporary variable> in <list of length 6>:
    print("Hello World!")

Notice that we need to iterate through a list of length 6, but we don’t necessarily care what is inside the list.

To create arbitrary collections of any length, we can pair our for loops with the Python built-in function range().

We can then use the range() function directly in our for loops as the collection to perform a six-step iteration:

for temp in range(6):
    print("Hello World!")

Would output:

Hello World!
Hello World!
Hello World!
Hello World!
Hello World!
Hello World!