Object Behavior

Describing Object Behavior

• In Python, everything is an object:

  • Integers are objects
  • Strings are objects
  • Lists are objects
  • Etc.

• Objects are generally classified according to:

  • Their behavior
  • The features that they implement
• Notice, there is overlap between these two properties

• For example, these objects have similar behavior:

  1. Strings
  2. Lists
  3. Tuples
  4. Xrange
• These objects are called sequence types
• Specifically, each sequence type is grouped together only because they support a common set of sequence operations
• For example, we can call $s[n]$ and $len(s)$ on sequence types

Introducing Special Methods

• All basic interpreter operations are implemented using special object methods
• These special methods always are preceded and followed by two underscores ( __ )
• These methods are automatically triggered by the interpreter during program execution
• The following examples are operations that map to internal methods:

$$x+y \quad \to \quad x.\text{\textunderscore \textunderscore add}(y)\text{\textunderscore \textunderscore}$$ $$x[k] \quad \to \quad x.\text{\textunderscore \textunderscore getitem}(k)\text{\textunderscore \textunderscore}$$

• Evidently, the behavior of each data type depends entirely on the set of special methods that it implements

References

• Python Essential Reference