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
A type is a set of values and operations that can be performed on those values.
Two of Python's numeric types:
-
int: integer
For example:3,4,894,0,-3,-18 -
float: floating point number (an approximation to a real number)
For example:5.6,7.342,53452.0,0.0,-89.34,-9.5
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
