.format() can be used in a number of ways.

Let's say, you're writing a func in a letter guessing game, where you want it to print out each wrong strike:

Here for ex: good_choice = [] #good_choice is a list
bad_choice = [] # And so is bad_choice

def draw(bad_choice, good_choice, secret_word): # The func. draw holds these arguments inside the bracket

print("Strikes: {}/7.".format(len(bad_choice)))   # Here I "formatted" {} by the len (length) of bad_choice

So for each bad_choice the player enters, a line will print out, i.e. :

The first strike : "Strikes: 1/7"

2nd strike : "Strikes: 2/7"

And so on. So here, I used .format() to print out each strike made

Hope this helps.

Think of .format as the "fill in the blank" function.

Where the string it is used on has a "blank" (a placeholder identified by braces), the .format function will replace that "blank" with a passed argument. Examples:

name = "Joe"
food = "cheese"
print("The customer's name is {}".format(name));  # will print "The customer's name is Joe."
print("{} likes to eat {}.".format(name, food))   # will print "Joe likes to eat cheese."