Calculator in command line using python programming language

University of the People Python fundamental

Chapter 5

Conditionals and recursion The main topic of this chapter is the if statement, which executes different code depending on the state of the program. But first I want to introduce two new operators: floor division and modulus. 5.1 Floor division and modulus The floor division operator, //, divides two numbers and rounds down to an integer. For example, suppose the run time of a movie is 105 minutes. You might want to know how long that is in hours. Conventional division returns a floating-point number:

minutes = 105 minutes / 60 1.75 But we don’t normally write hours with decimal points. Floor division returns the intege To get the remainder, you could subtract off one hour in minutes: remainder = minutes - hours * 60 remainder 45 An alternative is to use the modulus operator, %, which divides two numbers and returns the remainder. remainder = minutes % 60 remainder 45 The modulus operator is more useful than it seems. For example, you can check whether one number is divisible by another—if x % y is zero, then x is divisible by y

If you are using Python 2, division works differently. The division operator, /, performs floor division if both operands are integers, and floating-point division if either operand is a float.

5.2 Boolean expressions

A boolean expression is an expression that is either true or false. The following examples use the operator ==, which compares two operands and produces True if they are equal and False otherwise:

5 == 5 True 5 == 6 False True and False are special values that belong to the type bool; they are not strings: type(True) type(False) The == operator is one of the relational operators; the others are: x != y # x is not equal to y x > y # x is greater than y x < y # x is less than y x >= y # x is greater than or equal to y x <= y # x is less than or equal to y Although these operations are probably familiar to you, the Python symbols are different from the mathematical symbols. A common error is to use a single equal sign (=) instead of a double equal sign (==). Remember that = is an assignment operator and == is a relational operator. There is no such thing as =< or =>.

5.3 Logical operators

There are three logical operators: and, or, and not. The semantics (meaning) of these operators is similar to their meaning in English. For example, x > 0 and x < 10 is true only if x is greater than 0 and less than 10. n%2 == 0 or n%3 == 0 is true if either or both of the conditions is true, that is, if the number is divisible by 2 or 3.