2.1.4.5 Variables - data-shaped boxes

Assigning a new value to an already existing variable

How do you assign a new value to an already created variable? In the same way. You just need to use the equal sign.

The equal sign is in fact an assignment operator. Although this may sound strange, the operator has a simple syntax and unambiguous interpretation.

It assigns the value of its right argument to the left, while the right argument may be an arbitrarily complex expression involving literals, operators and already defined variables.

Look at the code below:

var = 1 print(var) var = var + 1 print(var)

The code sends two lines to the console:

1 2

output

The first line of the snippet creates a new variable named var and assigns 1 to it.

The statement reads: assign a value of 1 to a variable named var.

We can say it shorter: assign 1 to var.

Some prefer to read such a statement as: var becomes 1.

The third line assigns the same variable with the new value taken from the variable itself, summed with 1. Seeing a record like that, a mathematician would probably protest - no value may be equal to itself plus one. This is a contradiction. But Python treats the sign = not as equal to, but as assign a value.

So how do you read such a record in the program?

Take the current value of the variable var, add 1 to it and store the result in the variable var.

In effect, the value of variable var has been incremented by one, which has nothing to do with comparing the variable with any value.

Do you know what the output of the following snippet will be?

var = 100 var = 200 + 300 print(var)