Objects

• Functions or methods that change an object inplace should return None to make it clear to the caller that the object itself is changed, and no new object was created.

Object references

• Virtually, each data item is an object of a specific type or class in python.

Object identity

• A unique identifier is given to each created object.
  • id(<object>) returns the object’s integer identifier.

# Multiple references to a single object
n = 300
m = n # n -> 300 <- m

# Single reference to a single object
n = 300
m = 400 # n -> 300 & m -> 400

# Ophaned object
n = 300 # n -> 300
n = 200 # n -> 200, 300 # where 300 is the orphaned

Smaller integer values

• For optimization, the interpreter creates objects for the integers in the range [-5, 256] at startup, and then reuses them during program execution. Thus, when you assign separate variables to an integer value in this range, they will reference the same object.

m = 30
n = 30
id(m) # 1405569120
id(n) # 1405569120

Immutable and mutable objects

1. Immutable objects

• int
• float
• bool
• string
• bytes
• tuple
• frozenset
• None

2. Mutable objects

• list
• dict
• set
• byteArray
• objects
• functions
• almost everything else!

Scalar and numeric objects

1. Scalar types

• Single value types
  • None
  • str
  • bytes
  • float
  • bool
  • int

2. Numeric types

• int
• float