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Python as a Calculator

Arithmetic Operators

Operator Operation Expression English description Result
+ addition 11 + 56 11 plus 56 67
- subtraction 23 - 52 23 minus 52 -29
* multiplication 4 * 5 4 multiplied by 5 20
** exponentiation 2 ** 5 2 to the power of 5 32
/ division 9 / 2 9 divided by 2 4.5
// integer division 9 // 2 9 divided by 2 4
% modulo (remainder) 9 % 2 9 mod 2 1

Types int and float

type is a set of values and operations that can be performed on those values.

Two of Python's numeric types:

Arithmetic Operator Precedence

When multiple operators are combined in a single expression, the operations are evaluated in order of precedence.

Operator Precedence
** highest
- (negation)  
*, /, //, %  
+ (addition), - (subtraction) lowest

Syntax and Semantics

Syntax: the rules that describe valid combinations of Python symbols

Semantics: the meaning of a combination of Python symbols is the meaning of an instruction — what a particular combination of symbols does when you execute it.

Errors

A syntax error occurs when we an instruction with invalid syntax is executed. For example:

>>> 3) + 2 * 4
SyntaxError: invalid syntax

A semantic error occurs when an instruction with invalid semantics is executed. For example:

>>> 89.4 / 0
Traceback (most recent call last):
  File "", line 1, in
    89.4 / 0
ZeroDivisionError: float division by zero