Python type() Function

Python’s built-in type() function has two purposes. First, you can pass an object as an argument to check the type of this object. Second, you can pass three arguments—name, bases, and dict—to create a new type object that can be used to create instances of this new type.

Python type() Function Visual Explanation

Usage

Learn by example! Here’s an example on how to use the type() built-in function.

First, here’s how to use the type() function with one argument to check the type of a given object:

>>> type(42)
<class 'int'>
>>> type('Finxter')
<class 'str'>

Second, you can pass three arguments name, bases, and dict to create a new type:

>>> porsche = type('Car', (object,), {'speed': 100, 'electric':False})
>>> porsche
<class '__main__.Car'>
>>> porsche.speed
100
>>> porsche.electric
False

Let’s dive deeper into the powerful type() function to learn about it’s powerful features and usages!

Video type()

Let’s dive into the syntax of type() :

  • Syntax type() with one argument to check class of object
  • Syntax type() with three arguments to create new instance

Syntax type() with One Argument to Check Class of Object

Syntax: 
type(object)         # Returns class representation of object
ArgumentsobjectObject to be checked for type.
Return ValuestringReturns string representation of the object‘s class.

An example is the following:

>>> type(42)
<class 'int'>
>>> type('Finxter')
<class 'str'>

In both cases, a string representation of the object’s class is returned.

Syntax type() with Three Arguments to Create New Instance

Syntax: 
type(name, bases, dict)         # Create a new instance with class name, base classes as defined in bases, and initial attributes as defined in dict
ArgumentsnameNew instance has this class name.
basesA tuple of one or more base classes. For example, the tuple(object,) indicates that it only inherits from the base class object.
dictDictionary mapping attribute names to attribute values.
Return ValuenameReturns a new instance of class name as defined in the argument list.

An example is the following:

>>> porsche = type('Car', (object,), {'speed': 100, 'electric':False})
>>> porsche
<class '__main__.Car'>
>>> porsche.speed
100
>>> porsche.electric
False

If you want to create another instance of the class car, you’d need to do some copy&paste work:

>>> tesla = type('Car', (object,), {'speed': 100, 'electric': True})
>>> tesla.electric
True

To avoid this, you could also create a new lambda function to one-linerize the object creation process with type():

>>> new_car = lambda attributes: type('Car', (object,), attributes)
>>> porsche = new_car({'speed':100, 'electric': False})
>>> tesla = new_car({'speed': 100, 'electric': True})
>>> porsche.electric
False
>>> tesla.electric
True

Interactive Shell Exercise: Understanding type()

Consider the following interactive code:

Exercise: Which type does the porsche instance have? Run to check!


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Summary

Python’s built-in type() function has two purposes.

  • First, you can pass an object as an argument to check the type of this object.
  • Second, you can pass three arguments—name, bases, and dict—to create a new type object that can be used to create instances of this new type.

First, here’s how to use the type() function with one argument to check the type of a given object:

>>> type(42)
<class 'int'>
>>> type('Finxter')
<class 'str'>

Second, you can pass three arguments name, bases, and dict to create a new type:

>>> porsche = type('Car', (object,), {'speed': 100, 'electric':False})
>>> porsche
<class '__main__.Car'>
>>> porsche.speed
100
>>> porsche.electric
False

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