Python isinstance list or tuple

How to Check Type of Variable in Python

In this tutorial, we’ll learn about getting and testing the type of variables by using two different ways, and finally, we’ll know the difference between these two ways.

1. Checking Variable Type With Type() built-in function

what is type()

type() is a python built function that returns the type of objects

syntax

As you can see, in the above code we have many different variables,
now let’s get the type of these variables.

If you want to know all types of objects in python, you’ll find it in the final part of the article.

Example 2: checking if the type of variable is a string

let’s say that you want to test or check if a variable is a string, see the code bellow

As you can see, the code works very well, but this is not the best way to do that.
Remember!, if you want to check the type of variable, you should use isinstance() built function.

2. Checking Variable Type With isinstance() built-in function

what is isinstance()

The isinstance() is a built-in function that check the type of object and return True or False

sytnax

example 1: checking variables type

 #check if "list_var" is list print(isinstance(list_var, list)) #check if "string_var" is tuple print(isinstance(string_var, tuple)) #check if "tuple_var" is tuple print(isinstance(tuple_var, tuple)) #check if "dictionry_var" is dictionary print(isinstance(dictionry_var, dict)) 

if you want to get type of object use type() function.

if you want to check type of object use isinstance() function

4. Data Types in Python

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Python isinstance() function explained with examples

The Python’s isinstance() function checks whether the object or variable is an instance of the specified class type or data type.

For example, isinstance(name, str) checks if name is an instance of a class str .

Table of contents

How To Use isinstance() Function in Python

Let’s see the syntax first before moving to the example.

isinstance(object, classinfo)

• It takes two arguments, and both are mandatory.
• The isinstance() function checks if the object argument is an instance or subclass of classinfo class argument

Using isinstance() function, we can test whether an object/variable is an instance of the specified type or class such as int or list. In the case of inheritance, we can checks if the specified class is the parent class of an object.

1. Pass object to isinstance() Pass the variable you want to check as object argument to the isinstance() . Here the object can be any class object or any variable name
2. Specify the Class or Type name as a classinfo argument For example, isinstance(x, int) to check if x is an instance of a class int .
   classinfo is a type name or Class name you want to check against the variable. Here you can specify data type name or Class name.
   You can also pass multiple classes/types in a tuple format. For example, you can pass int , str , list , dict , or any user-created class.
3. Execute your operation, If result is True The isinstance() returns True if an object or variable is of a specified type otherwise False.

Example

Using isintance() we can verify whether a variable is a number or string. Let’s assume variable num = 90 , and you want to check whether num is an instance of an int type.

num = 90 result = isinstance(num, int) if result: print("Yes") else: print("No")

As we can see in the output, the isinstance() returned True because num hold an integer value.

Note: If the classinfo argument is not a Class, type, or tuple of types, a TypeError exception is raised.

isinstance() With Built-In Types

As you know, Every value (variable) in Python has a type. In Python, we can use different built-in types such as int , float , list, tuple, strings, dictionary. Most of the time, you want to check the type of value to do some operations. In this case, isinstance() function is useful.

# Check if 80 is an instance of class int number = 80 print(isinstance(number, int)) # output True print(isinstance(number, float)) # output False pi = 3.14 # Check 3.14 is an instance of class float print(isinstance(pi, float)) # Output True # Check if (1 + 2j) is an instance of complex complex_num = 1 + 2j print(isinstance(complex_num, complex)) # Output True # Check if 'PYnative' is an instance of class string name = "PYnative.com" print(isinstance(name, str)) # Output True # Check if names is an instance of class list names = ["Eric", "Scott", "Kelly"] print(isinstance(names, list)) # Output True # Check if student_report is an instance of class dict student_report = print(isinstance(student_report, dict)) # Output True # Check if names is an instance of class tuple names = ("Sam", "Kelly", 'Emma') print(isinstance(names, tuple)) # Output True # Check if numbers is an instance of class tuple numbers = print(isinstance(numbers, set)) # Output True

Note: If we use the isinstance() with any variable or object with a None , it returns False . Let see the simple example of it.

var = None # empty but not None s1 = '' print(isinstance(var, float)) # Output False print(isinstance(s1, str)) # Output True

isinstance() With Multiple Classes

You can also check the instance with multiple types. Let’s say you have a variable, and you wanted to check whether it holds any numeric value or not, for example, a numeric value can be an int or float .

To verify whether a variable is an instance of one of the specified types, we need to mention all types in a tuple and pass it to the classInfo argument of isinstance() .

def check_number(var): if isinstance(var, (int, float)): print('variable', var, 'is instance of numeric type') else: print('variable', var, 'is not instance of numeric type') num1 = 80 check_number(num1) # Output variable 80 is instance of numeric type num2 = 55.70 check_number(num2) # Output variable 55.7 is instance of numeric type num3 = '20' check_number(num3) # Output variable '20' is not instance of numeric type 

isinstance() With Python Class

The isinstance() works as a comparison operator, and it compares the object with the specified class type.

You can verify if the emp object is an instance of a user-defined class Employee using the isinstance() function. It must return True.

class Employee: def __init__(self, name, salary): self.name = name self.salary = salary class Person: def __init__(self, name, sex): self.name = name self.sex = sex emp = Employee("Emma", 11000) per = Person("Brent", "male") # Checking if a emp object is an instance of Employee print(isinstance(emp, Employee)) # Output True # Checking if the per object is an instance of Employee print(isinstance(per, Employee)) # Output False

isinstance() function With Inheritance

The object of the subclass type is also a type of parent class. For example, If Car is a subclass of a Vehicle, then the object of Car can be referred to by either Car or Vehicle. In this case, the isinstance(carObject, Vehicle) will return True .

The isinstance() function works on the principle of the is-a relationship. The concept of an is-a relationship is based on class inheritance.

The instance() returns True if the classinfo argument of the instance() is the object’s class’s parent class.

To demonstrate this, I have created two classes, Developer and PythonDeveoper. Here PythonDeveoper is a sub-class of a Developer class.

class Developer(object): # Constructor def __init__(self, name): self.name = name def display(self): print("Developer:", self.name, "-") class PythonDeveloper(Developer): # Constructor def __init__(self, name, language): self.name = name self.language = language def display(self): print("Python Developer:", self.name, "language:", self.language, "-") # Object of PythonDeveloper dev = PythonDeveloper("Eric", "Python") # is PythonDeveloper object an instance of a PythonDeveloper Class print(isinstance(dev, PythonDeveloper)) # Output True # is python_dev object an instance of a Developer Class print(isinstance(dev, Developer)) # Output True

Note: The isinstance() function is beneficial for casting objects at runtime because once you get to know the given class is a subclass of a parent class, you can do casting appropriately if required.

isinstance with Python list

As you know, a Python list is used to store multiple values at the same time. These values can be of any data type like numbers, strings, or any Class objects.

In this section, we will test the following operations with the Python list using the isinstance() function:

• Checking if an object is of type list in python.
• Check if an element of a list is a list.
• Verify if elements of a list are numbers or strings.
• Python check if all elements of a list are the same type

Checking if an object is an instance of a list type

sample_list = ["Emma", "Stevan", "Brent"] res = isinstance(sample_list, list) print(sample_list, 'is instance of list?', res) # Output 'Emma', 'Stevan', 'Brent'] is instance of list? True

Check if an element of a list is a nested list

To check if one of the elements in the list is itself a list. For example, you have the following list, Use the isinstance() to verify if the list contains a nested list

sampleList = ['Emma', 'Stevan', ['Jordan', 'Donald', 'Sam']]

Iterate a list and verify each element’s class, and if it a list type, we can say that the list contains a nested list.

sample_list = ['Emma', 'Stevan', ['Jordan', 'Donald', 'Sam']] for item in sample_list: if isinstance(item, list): print("Yes", item, 'is a nested list') # Output Yes ['Jordan', 'Donald', 'Sam'] is a nested list

Check if elements of a list are numbers or strings

Check each element’s type with multiple numeric types such as int , float , and complex using the isinstance() function.

To find all string variables, Check each element’s type with str type.

sample_list = ['Emma', 'Stevan', 12, 45.6, 1 + 2j, "Eric", ] number_list = [] string_list = [] for item in sample_list: if isinstance(item, (int, float, complex)): number_list.append(item) elif isinstance(item, str): string_list.append(item) # String List print(string_list) # Output ['Emma', 'Stevan', 'Eric'] # Number list print(number_list) # Output [12, 45.6, (1+2j)]

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About Vishal

I’m Vishal Hule, Founder of PYnative.com. I am a Python developer, and I love to write articles to help students, developers, and learners. Follow me on Twitter

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