2.1.6.5 How to talk to a computer

More about input() and type casting

Having a team consisting of the trio input()-int()-float() opens up lots of new possibilities.

You'll eventually be able to write complete programs, accepting data in the form of numbers, processing them and displaying the results.

Of course, these programs will be very primitive and not very usable, as they cannot make decisions, and consequently are not able to react differently to different situations.

This is not really a problem, though; we'll show you how to overcome it soon.

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Our next example refers to the earlier program to find the length of a hypotenuse. Let's rewrite it and make it able to read the lengths of the legs from the console.

Check out the editor window - this is how it looks now.

The program asks the user twice for both legs' lengths, evaluates the hypotenuse and prints the result.

Run it and try to input some negative values.

The program - unfortunately - doesn't react to this obvious error.

Let's ignore this weakness for now. We'll come back to it soon.

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Note that in the program that you can see in the editor, the hypo variable is used for only one purpose - to save the calculated value between the execution of the adjoining line of code.

As the print() function accepts an expression as its argument, you can remove the variable from the code.

Just like this:

leg_a = float(input("Input first leg length: ")) leg_b = float(input("Input second leg length: ")) print("Hypotenuse length is", (leg_a**2 + leg_b**2) ** .5)

•  Sandbox

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leg_a = float(input("Input first leg length: "))

leg_b = float(input("Input second leg length: "))

hypo = (leg_a**2 + leg_b**2) ** .5

print("Hypotenuse length is", hypo)

• Console