Guessing and checking with conditionals

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• Conditionals are at the heart of machine learning.
• Python return Booleans when comparing two values, allowing you to use the result to decide what to do next.
• Checking for equality requires two equal signs (==).
• You can have your program make decisions about what code to run using if and else statements.

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Using conditionals to find factors

-A factor is a number that divides evenly into another number. -In Python you can use the modulo operator (%) to calculate the remainder when dividing two numbers. For example, if a % b equals zero, it means that b divides evenly into a.

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The wandering turtle

• We use Python's infinite while True loop, which always evaluates to True. This will make the turtle wander around without stopping.

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Creating a number-guessing game

Let's use conditionals to write an interactive number-guessing program that seems conscious. In this game I think of a number between 1 and 100, and you guess what the number is.

Making a random number generator

• Create numberGame.py: Import the random module and assign a random integer to a variable using the randint() function.

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Taking user input

• Ask the user for input so they can take a guess

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Converting user input to integers

• In Python, all input from users is always taken as a string. This means that if we want numbers as inputs, we have to convert them to an integer data type, so we can use them in operations.

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Using conditionals to check for a correct guess

• We use the if statement to compare the input to the content of number, and we use elif and else to decide what to do in each circumstance.

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Using a loop to guess again

• We can make a loop so that the program keeps asking for more guesses until the user guesses correctly. We use the while loop to keep looping until guess is equal to number, and then the program will print a success message and break out of the loop.
• Tip for guessing: Your next guess would be halfway between the number you guess and the top of the range. For each guess you're eliminating half the possible numbers.
• We can use this exact idea to find a very accurate value for the square root of a number.

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Finding square roots

• Square roots can be whole numbers (the square root of 100 is 10, for example), but many more are irrational numbers, which are never ending, never repeating decimals. They come up a lot in coordinate geometry when you have to find the roots of polynomials.
• Your calculator or computer uses an iterative method like the number guessing strategy!

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Writing the squareRoot() function

• The squareRoot() function takes three parameters: num (the number we want the square root of), low (the lowest limit num can be), and high (the upper limit to num). If the number you guess squared is equal to num, we just print it and break out of the loop. This may happen for a whole number, but not for an irrational number.
• Next, the program cheks wheter the number you guess squared is greater than num, in which case you should guess lower. We shorten our range to go from low to the guess by replacing high with the guess. The only other possibility is if the guess is too low, in wich case we shorten our range to go from the guess to high by replacing low with the guess.
• The program keeps repeating the process as many times as we want (20 in this case).