What does {0} mean in this Python string?

Question

The following program uses {0} in a string, and I'm not sure how it works, it came up in an online tutorial about iteration for Python, and I can't seem to find anywhere explaining it.

import random  number = random.randint(1, 1000) guesses = 0  print("I'm thinking of a number between 1 and 1000.")  while True:    guess = int(input("\nWhat do you think it is? "))    guesses += 1      if guess > number:         print("{0} is too high.".format(guess))     elif guess < number:          print("{0} is too low.".format(guess))     else:         break  print("\nCongratulations, you got it in {0} guesses!\n".format(guesses)) 

Thank you!

Answer 1

It's an indicator to the format method that you want it to be replaced by the first (index zero) parameter of format. (eg "2 + 2 = {0}".format(4))