Questions and answers

Questions and answers

A programmer writes a program and the program asks questions.

A computer executes the program and provides the answers. The program must be able to react according to the received answers.

Fortunately, computers know only two kind of answers:

• yes, this is true
• no, this is false

You will never get a response like Let me think...., I don't know, or Probably yes, but I don't know for sure.

To ask questions, Python uses a set of very special operators. Let's go through them one after another, illustrating their effects on some simple examples. 

Comparison: equality operator

Question: are two values equal?

To ask this question, you use the == (equal equal) operator.

Don't forget this important distinction: 

• = is an assignment operator, e.g., a = b assigns a with the value of b
• == is the question are these values equal? a -== b compares a and b

It is a binary operator with left-sided binding. It needs two arguments and checks if they are equal.

Exercises

Now let's ask a few questions. Try to guess the answers.

Question #1: What is the result of the following comparison? 

2 == 2

True - of course, 2 is equal to 2. Python will answer True (remember this pair of predefined literals, True and False - they're Python keywords, too).

Question #2: What is the result of the following comparison? 

2 == 2.

The question is not as easy as the first one. Luckily, Python is able to convert the integer value into its real equivalent, and consequently, the answer is True.

Question #3: What is the result of the following comparison?

1 == 2 

This should be easy. The answer will be(or rather, always is) False.