So I want to introduce one more operation on strings, which we'll find very useful, which is the Find operation. It gives us the way in a big string to find some sub-string that we're looking for. The way we use Find is a little different from the way we've used other operators so far. Because Find is actually a method, and what that means is it's a built in procedure provided by Python. We'll be able to define our own procedures soon, we'll get to that in unit two. Find is a procedure that operates on strings, so we use it by having a string followed by .find, followed by a parentheses, then we pass in another string. Which is the string that we want to find in the first string. And the output of Find is the position in the string where that sub-string is found, the first occurrence of the string. So, if that string happens to occur in more places than one in the input string, the result of find is always going to give us the position. That's the number where the first occurrence of the sub-string occurs. So the output of using Find will be the first position in the search string, which is this blue string right here, where the target string, which is the purple string, occurs. So that will be a number. If the target string is not a found anywhere in the search string, then the output would be negative 1. So let's try a few examples to understand how that works and we'll do this in the Python interpreter. Here I've initialized the variable Pythagoras to hold the string here that's been attributed to Pythagoras. We don't know if he really said it. But it says there's a geometry in the humming of strings, there is music in the spacing of spheres. So now, we have that variable initialized, so I'm going to invoke Find, using Pythagoras as the string that we're searching in, and that's the value that we initialized it to with a string, passing in as the search string the string string. When we run this, we see that we get 40 as the result. If we counted, this is position 0, we would see string starting at position 40. Since I don't want to count that far, we can use our indexing to see if that's right. So let's print Pythagoras starting from index 40, we could print all the way to the end using a colon. And, when we run that, we see that it starts with string which is what we found with the Find. We can search for other positions if we search for Pythagoras the single letter T. Well that matches the beginning, so we should find the resulted position 0 which is what we get and we can look for sphere. [BLANK_AUDIO] That will match sphere at the end. We get position 86. Let's print the quote from position 86. And we see the end of the quote starting from sphere. [SOUND] If we search for a string that's not in the string that we're using as the search string, so let's look for say, algebra, which was not in the quote from Pythagoras, we get the output negative one. That means the string was not found.