Numbers

Prefixes

Prefixes convert types like binary, hex and octal into int.

  • No prefix for decimal​

  • Prefix with 0b, B for binary (ex. 0b10 == 2)​

  • Prefix with 0x, X for hex (ex. 0xF == 15)​

  • Prefix with 0o, O for octal (ex. 0o100 == 64)​

Types

  • int (integer)
    • Equivalent to C-Longs in Python 2 and non-limited in Python 3

  • Long

    • Long integers of non-limited length. Exist only in Python 2

  • Float (decimal, hex, octal)

    • Floating point numbers. Equivalent to C-Doubles

  • Complex

    • Complex numbers, ex:
    x = 1.5 + j
y = 2
z = x + y
print z
#Output: (3.5+5j)

Numbers are IMMUTABLE!

Numbers cannot be modified in place. Be sure to either reassign your current variable or assign the number to a new variable.

Bool (True or False)

Bools are a subclass of int. This was done around Python 2.2 to allow previous implementations of bools (0 and 1) to continue working… especially so with C code that utilizes Pylint_Check()

Truth Value Testing

  • The following will evaluate to False:

    • False
    • zero numeric type- 0 0.0 0
    • None
    • empty sequence – ‘’ () []
    • empty mapping- {}
    • instances of user defined classes (will get into later)​

  • The following will evaluate to True: Everything else, not limited to but including–

    • True, 1

    • any number that is less than or greater than 0... but not 0

    • non-empty sequence/mapping, etc

Operators

There are some differences between Python and many other languages that need to be brought to light. Increment operators (x++, y--, etc) do not exist in Python. To increment in Python, you can use shorthand: a += 1, x -= 5, z *= 2, etc

Operator Description Example Result
+ Addition 4 + 5 9
- Subtraction 10 - 5 5
* Multiplication 4 * 2 8
/ Division* 3 / 2 Py2(1) Py3(1.5)
// Floor Division 3.0 // 1.0 1 (~int division)
% Modulus (remainder) 4 % 2 0
** Exponentiation 4 ** 2 16

*3.0 / 2 will return 1.5 for both Python 2 and Python 3

Order of Operations

Operation Precedence Extra
() 1 Anything in brackets is first
** 2 Exponentiation
-x, +x 3
*, /, %, // 4 Will evaluate left to right
+, - 5 Will Evaluate left to right
<, >, <=, >=, !=, == 6 Relational Operators
Logical Not 7
Logical And 8
Logical Or 9

Type Conversion

int(‘x’, base) # Returns x as base integer​
float(x) # Returns x as float​
complex(real, imag) # Returns complex number​
chr(x) # Returns string of one character for x as ASCII​
ord(x) # Returns ASCII value for x as string of one char​
hex(x) # Returns x as hex​
oct(x) # Returns x as octal​

There are some differences between Python 2 and Python 3 numbers. The biggest difference being the removal of the Long Type in Python 3.

Lab 2B and 2C

Download the following files and follow the instructions within.

  • 2A: numbers.py
  • 2B: tax_calc.py

results matching ""

    No results matching ""