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Symbol Purpose Example Output
a = 5
Floor division first and then assigns the result to
//= b = 10
the left-hand side operand.
b //= a 2
a = 5
Remainder of a number first and then assigns
%= b = 10
the result to the left-hand side operand.
a %= b 5
a = 2
Exponential of a number first and then assigns
**= b = 4
the result to the left-hand side operand.
a **= b 16
Operator Precedence
An expression is made up of values, variables, operators and functions. For example,
x-5+6 is an expression
To evaluate an expression with multiple operators, Python follows an order of precedence. This order can be
altered by writing an expression within parentheses.
The order of precedence in descending order is listed below:
Order of Precedence Operators
1 ()
2 **
3 */%//
4 +-
5 <= < > >=
6 == !=
7 = %= /= //= -= += *= **=
8 not, and, or
If an expression contains two or more operators with the same precedence, then the order of evaluation is from
left to right, except for exponential (**) which is always from right to left. For example,
• 10 – 2 + 3 – 3 will be evaluated from left to right as + and – has the same order of precedence. So, the answer
will be 10 – 2 will be 8 + 3 will be 11 – 3 will be 8.
• 2 ** 3 ** 2 will always be evaluated from right to left. It will be calculated as 2 ** (3 ** 2) and not as
(2 ** 3) ** 2. So, the answer will be 512.
Variables
A variable is a name given to a memory location to hold a specific value. It is just like a container that can hold
any type of data that can be changed later in the program.
Variable has:
• A name that follows the identifier naming conventions and is case-sensitive.
• A value that can be integer, float, string, boolean, etc.
Introduction to Python 231

