Dec. 7, 2012, 6:42 p.m. by Rosalind Team

**Topics**:
Introductory Exercises,
Programming

## Variables and Some Arithmetic

One of the most important features of any programming language is its ability to manipulate variables. A variable is just a name that refers to a value; you can think of a variable as a box that stores a piece of data.

In Python, the basic data types are strings and numbers. There are two types of numbers: integers (both positive and negative) and floats (fractional numbers with a decimal point). You can assign numbers to variables very easily. Try running the following program:

a = 324 b = 24 c = a - b print 'a - b is', cIn the above code, a, b, and c are all integers, and 'a - b is' is a string. The result of this program is to print:

a - b is 300You can now use all common arithmetic operations involving numbers:

- Addition:
`2 + 3 == 5`

- Subtraction:
`5 - 2 == 3`

- Multiplication:
`3 * 4 == 12`

- Division:
`15 / 3 == 5`

- Division remainder:
`18 % 5 == 3`

- Exponentiation:
`2 ** 3 == 8`

It is important to note that if you try to divide two integers, Python always rounds

downthe result (so`18/5 == 3`

).To obtain a precise result for this division, you need to indicate floating point division; either of the following expressions results in a "float" data type:

`18.0/5 == 3.6`

or`float(18)/5 == 3.6`

In Python, the single equals sign (

`=`

) means "assign a value to a variable". For example,`a = 3`

assigns 3 to the integer a. In order to denote equality, Python uses the double equals sign (`==`

).In Python, a string is an ordered sequence of letters, numbers and other characters. You can create string variables just like you did with :

a = "Hello" b = "World"Notice that the string must be surrounded by " or ' (but not a mix of both). You can use quotes inside the string, as long as you use the opposite type of quotes to surround the string, e.g.,

`a = "Monty Python's Flying Circus"`

or`b = 'Project "Rosalind"'`

.String operations differ slightly from operations on numbers:

a = 'Rosalind' b = 'Franklin' c = '!' print a + ' ' + b + c*3Output:

Rosalind Franklin!!!

Given: Two positive integers

Return: The integer corresponding to the square of the hypotenuse of the right triangle whose
legs have lengths

**Notes**:

- The dataset changes every time you click "Download dataset".
- We check only your final answer to the
*downloaded*dataset in the box below, not your code itself. If you would like to provide your code as well, you may use the upload tool. Please also note that the correct answer to this problem will not in general be 34; it is simply an example of what you should return in the specific case that the legs of the triangle have length 3 and 5.

3 5

34