Is there any Python object inspector?

Python doesn't have a built-in object inspector, but it provides several powerful functions and modules for examining objects. Functions like type(), help(), dir(), vars(), and the inspect module help you discover attributes, properties, and methods of any object.

Additional functions like id(), getattr(), hasattr(), globals(), locals(), and callable() are useful for examining object internals. Let's explore these inspection techniques using a simple class example.

Sample Class for Demonstration

First, let's create a Height class that we'll use throughout our examples ?

class Height:
    """
    A height class that describes height in inches.
    """
    def __init__(self, inches):
        """
        Assign the amount of inches to the height object
        """
        self.inches = inches
    
    def to_centimeter(self):
        """
        Convert the inches to centimeters.
        1 inch = 2.54 centimeter
        """
        return self.inches * 2.54

Using type() Function

The type() function returns the exact type of an object ?

Syntax

type(object)

Example

class Height:
    """
    A height class that describes height in inches.
    """
    def __init__(self, inches):
        self.inches = inches
    
    def to_centimeter(self):
        return self.inches * 2.54

h = Height(2)
print("Type of h:", type(h))
print("Type of Height:", type(Height))

Type of h: <class '__main__.Height'>
Type of Height: <class 'type'>

Using help() Function

The help() function provides detailed documentation about an object, including methods and docstrings ?

class Height:
    """
    A height class that describes height in inches.
    """
    def __init__(self, inches):
        """
        Assign the amount of inches to the height object
        """
        self.inches = inches
    
    def to_centimeter(self):
        """
        Convert the inches to centimeters.
        1 inch = 2.54 centimeter
        """
        return self.inches * 2.54

help(Height)

Help on class Height in module __main__:

class Height(builtins.object)
 |  Height(inches)
 |  
 |  A height class that describes height in inches.
 |  
 |  Methods defined here:
 |  
 |  __init__(self, inches)
 |      Assign the amount of inches to the height object
 |  
 |  to_centimeter(self)
 |      Convert the inches to centimeters.
 |      1 inch = 2.54 centimeter
 |  
 |  ----------------------------------------------------------------------
 |  Data descriptors defined here:
 |  
 |  __dict__
 |      dictionary for instance variables (if defined)
 |  
 |  __weakref__
 |      list of weak references to the object (if defined)

Using dir() Function

The dir() function returns a list of all attributes and methods available for an object ?

class Height:
    def __init__(self, inches):
        self.inches = inches
    
    def to_centimeter(self):
        return self.inches * 2.54

h = Height(24)
attributes = dir(h)
print("Total attributes:", len(attributes))
print("Custom method:", 'to_centimeter' in attributes)
print("Instance variable:", 'inches' in dir(h))

Total attributes: 27
Custom method: True
Instance variable: False

Using hasattr() Function

The hasattr() function checks if an object has a specific attribute ?

Syntax

hasattr(object, name)

Example

class Height:
    def __init__(self, inches):
        self.inches = inches
    
    def to_centimeter(self):
        return self.inches * 2.54

h = Height(24)
print("Has 'to_centimeter' method:", hasattr(h, "to_centimeter"))
print("Has 'inches' attribute:", hasattr(h, "inches"))
print("Has 'weight' attribute:", hasattr(h, "weight"))

Has 'to_centimeter' method: True
Has 'inches' attribute: True
Has 'weight' attribute: False

Using vars() Function

The vars() function returns the __dict__ attribute of an object, showing instance variables ?

class Height:
    def __init__(self, inches):
        self.inches = inches
        self.unit = "inches"
    
    def to_centimeter(self):
        return self.inches * 2.54

h = Height(24)
print("Instance variables:", vars(h))

Instance variables: {'inches': 24, 'unit': 'inches'}

Comparison of Inspection Methods

Conclusion

Python provides excellent object inspection capabilities through built-in functions like type(), help(), dir(), hasattr(), and vars(). These functions help developers understand object structure, available methods, and attributes during development and debugging.