Python vars()

The Python vars() function is a built-in function that returns the __dict__ attribute of a given object, which is a dictionary containing the object’s writable attributes. It accepts a single optional parameter: any object that has a __dict__ attribute, such as a module, class, or instance. When called without arguments, it behaves like locals() and returns a dictionary of the current local symbol table. The function returns a dictionary where keys are attribute names (as strings) and values are the corresponding attribute values. The vars() function is particularly useful for debugging and introspection, allowing you to inspect all attributes of an object at runtime. A real-world example is logging the state of a configuration object by converting it to a dictionary with vars(config) for serialization or display. It complements dir(), which lists all attribute names including inherited ones, while vars() only returns the instance’s own attributes.

What does vars() return?

The vars() function returns a dictionary (__dict__) of the object’s writable attributes. When called without arguments, it returns the local symbol table as a dictionary.

When should you use vars()?

Use vars() when you need to inspect or iterate over the attributes of an object as a dictionary, particularly for debugging, serialization, or dynamically accessing an object’s state.

The syntax of the vars() function is :

vars(object)

vars() parameters

vars() function takes only one parameter as argument:

• object - Any object having the __dict__ attribute or module,class ,instance.

Example 1: How to use vars() function on python?

class Dog:
  def __init__(self, a = 4, b = 8):
    self.a = a
    self.b = b
  
object = Dog()
print(vars(object))

Output:

{'a': 4, 'b': 8}

The __dict__ attribute is a dictionary containing the specific object’s changeable attributes.

Common Use Cases

A common use case for vars() is converting an object’s attributes into a dictionary for JSON serialization, such as json.dumps(vars(user)) to send object data over an API. Another practical scenario is debugging by printing the complete state of an object with print(vars(my_object)) to see all current attribute values at a glance. It is also useful in ORM-like patterns where you need to iterate over an object’s fields to generate SQL statements or form fields dynamically, working alongside setattr() for attribute modification.

Rules of vars()

• If called without any parameters, it will return a dictionary containing the local symbol table.

• vars() will return the __dict__ attributes of the given object.
• If the object passed to vars() doesn’t have the __dict__ attribute, it raises a TypeError exception.