Python variables

Question

Hey, I'm trying to create a basic program that will generate a number based on variables entered by the user. The formula is

a = b / (c * d)

This is a formula for finding specific heat, whereas b=energy, c=mass, and d= change in temperature.

So my problem is that I'm not making this program for myself, otherwise I could just assign each variable a number- like:

b= 1200
c= 13
d= 2

And then do a = a = b / (c * d).

My goal though, is to create a program for others who don't already know the formula- so that they can simply enter the numbers themselves. Example- I want b = X. X is the number entered by the user of the program. However, I have to define X as a variable first- I want it to be unknown- or based on what a person enters. I don't want b, c, or d to have assigned values. It's a very basic scripting process I know, but I'm new to Python.

Thanks a lot.

Answer 1

b = float(raw_input("Please enter a value: "))
a = b / (c*d)
print a

raw_input() prompts the user for input, assuming you're running this in the console

float() attempts to convert the parameter (in this case, the user input) to a float. the rest of it should be pretty straightforward.

Give that a try. Welcome to Python :)

Answer 2

The most simple approach is to precede the formula with the fragment

b = input("Enter b:")
c = input("Enter c:")
d = input("Enter d:")

A few things to note:

• this will require console IO, so you best start the script from a console
• input() causes the string entered to be eval()'ed, meaning that it gets processes as if it was a Python expression. This is useful for numbers, but may have confusing side effects; consider using raw_input(), along with float() instead.

Answer 3

I think you want something like this:

b = float(raw_input("Energy? "))
c = float(raw_input("Mass? "))
d = float(raw_input("Change in temperature? "))

print "Specific heat: %f" % (b / (c * d))

• raw_input() prompts the user and returns the inputted value
• float() converts the value to a float (if possible; if not, this will throw an exception and terminate the program)
• the "%f" in the last line formats the argument as a floating-point value, where "the argument" is the value of the expression following the % outside of the string (i.e. '(b / (c * d))')