2.6. Expressions

An expression is a combination of values, variables, and operators. A value all by itself is considered an expression, and so is a variable, so the following are all legal expressions (assuming that the variable x has been assigned a value):

17
x
x + 17

If you type an expression in interactive mode, the interpreter evaluates it and displays the result:

1 + 1 print(1+1)

But in a script, an expression all by itself doesn’t do anything! This is a common source of confusion for beginners.

Type the following statements in the Python interpreter to see what they do:

5
x = 5
x + 1

csp-10-2-2: Which of the following is an expression?

• 5
• An expression is a combination of values, variables, and operators.
• x = 5
• An expression is a combination of values, variables, and operators.
• x + 1
• An expression is a combination of values, variables, and operators.
• all of the above
• All of the above are correct! An expression is a combination of values, variables, and operators.
• none of the above
• An expression is a combination of values, variables, and operators.

csp-10-2-3: Click on the expression(s) that will **not** return a value when typed in an interpreter.Try typing these expressions in a python interpreter to see what they do.

12
x = 73
x + 12
x += 52    #using += is the same as writing out x = x + 52

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