python get type of variable with code examples

Python is a dynamic, object-oriented, general-purpose programming language that has enjoyed a tremendous rise in popularity over the years, largely due to its simplicity, ease of use, and versatility in a wide range of applications. One of the key features of Python is its dynamic typing system, which means that data types are inferred at runtime based on the value assigned to the variable. However, there are times when we need to determine the data type of a variable in our code, and that's what we'll be discussing in this article – how to get the type of a variable in Python with code examples.

Python dynamically infers the variable's data type based on the value assigned to it. For instance, if the assignment is a string, Python sets the data type of the variable as a string. If the value is a number, Python will determine the type based on whether it's an integer, float, or complex.

There are numerous built-in functions in Python that can be used to determine the type of a variable, and we'll be exploring some of them in this article.

  1. Using the type() function

The simplest way to obtain the data type of a variable is by using the type() function. The type() function in Python returns the data type of any given object. Here's an example code snippet:

a = 5
b = 5.3
c = "Hello, World!"
d = [1, 2, 3, 4]
e = {"key1": "value1", "key2": "value2"}

print(type(a))  # Output: <class 'int'>
print(type(b))  # Output: <class 'float'>
print(type(c))  # Output: <class 'str'>
print(type(d))  # Output: <class 'list'>
print(type(e))  # Output: <class 'dict'>
  1. Using the isinstance() function

The isinstance() function is used to determine whether an object is an instance of a specified class or not. Here's an example:

a = 5
b = "Hello, World!"

print(isinstance(a, int))   # Output: True
print(isinstance(b, str))   # Output: True
print(isinstance(a, str))   # Output: False
print(isinstance(b, int))   # Output: False
  1. Using the type annotations

With Python 3.5 and above, type annotations were introduced, which allowed developers to indicate the expected type of a variable. Here's an example code snippet:

def foo(a: int, b: str) -> float:
    result = 5.5
    return result

print(foo(5, 'Hello'))  # Output: 5.5
print(foo('Hello', 5))  # Output: TypeError

The above code defines a function that takes two arguments, an integer and a string, and returns a float. If you pass an argument that doesn't match the expected type, Python raises a TypeError.

  1. Using the class attribute

Every object in Python has an class attribute that represents the class to which it belongs. We can use this attribute to determine the type of a variable.

a = 5
b = "Hello, World!"
c = [1, 2, 3, 4]

print(a.__class__)   # Output: <class 'int'>
print(b.__class__)   # Output: <class 'str'>
print(c.__class__)   # Output: <class 'list'>
  1. Using the inspect module

The inspect module in Python is used to get information about classes, functions, and methods. We can use the getmembers() method of the inspect module to get the type of a variable.

import inspect

a = 5
b = "Hello, World!"
c = [1, 2, 3, 4]

print(inspect.getmembers(a))   # Output: (<class 'int'>, 5)
print(inspect.getmembers(b))   # Output: (<class 'str'>, 'Hello, World!')
print(inspect.getmembers(c))   # Output: (<class 'list'>, [1, 2, 3, 4])

Conclusion

In conclusion, Python's dynamic typing system is one of its biggest strengths, but there are times when we need to determine the type of a variable explicitly. Python provides numerous ways to accomplish this task, such as using the type() function, isinstance() function, type annotations, the class attribute, and the inspect module. As always, understanding the various tools available to a Python developer is critical in writing clean, efficient, and maintainable code.

  1. Using the type() function

The type() function is a built-in Python function that returns the data type of an object. It takes one argument, which can be any object. When called, type() returns a type object that represents the data type of the object.

For example, if we have a variable “x” that contains the value 42, we can determine its data type using the type() function like this:

x = 42
print(type(x))

The output of the code above will be: <class 'int'>

We can also use the type() function to determine the data type of more complex objects, such as functions or classes. For example, to determine the type of a function named “my_function”, we can call the type() function like this:

def my_function():
    return "Hello, world!"

print(type(my_function))

The output of the code above will be: <class 'function'>

  1. Using the isinstance() function

The isinstance() function is another built-in Python function that is used to determine the data type of an object. However, instead of returning the data type directly, isinstance() returns a Boolean value that indicates whether an object is an instance of a particular class or data type.

If the object is an instance of the specified class, isinstance() returns True. Otherwise, it returns False. Here is an example of how to use isinstance() to check whether a variable is an instance of a specific data type:

x = 42
print(isinstance(x, int))

The output of the code above will be: True

We can also use isinstance() to check whether an object is an instance of multiple classes or data types. For example:

x = 42
print(isinstance(x, (int, float)))

The output of the code above will be: True

  1. Using type annotations

Type annotations are a relatively new feature in Python 3 that allow developers to specify the data type of a variable, function parameter, or function return value using a special syntax.

Here is an example of how to use type annotations to specify the data type of a function parameter and return value:

def multiply(x: int, y: int) -> int:
    return x * y

In the code above, we have defined a function called multiply that takes two integer arguments (x and y) and returns an integer value. We did this using type annotations, which specify that the data type of x, y, and the return value is int.

Type annotations can also be used to specify the data type of variables and class attributes. For example:

x: str = "Hello, world!"

In the code above, we have created a variable called x and specified that its data type is a string using type annotations.

  1. Using the class attribute

Every object in Python has an class attribute that represents the class to which it belongs. By accessing the class attribute of an object, we can determine the data type of the object.

Here is an example of how to use the class attribute to determine the data type of a variable:

x = "Hello, world!"
print(x.__class__)

The output of the code above will be: <class 'str'>

We can also use the class attribute to determine the data type of more complex objects, such as functions or classes.

  1. Using the inspect module

The inspect module is a built-in Python module that provides advanced introspection capabilities. We can use the inspect module to determine the data type of an object by passing the object to the getmembers() function.

Here is an example of how to use the inspect module to determine the data type of a variable:

import inspect

x = "Hello, world!"
print(inspect.getmembers(x))

The output of the code above will be: [('add', <method-wrapper 'add' of str object at 0x7ff00f3e9350>), ('class', <class 'str'>), ('contains', <method-wrapper 'contains' of str object at 0x7ff00f3e9350>), … ]

In this example, we have imported the inspect module and passed the variable x to the getmembers() function. The getmembers() function returns a list of tuples that contain information about the object, including its data type.

Popular questions

  1. What is the type() function used for in Python?
    Answer: The type() function in Python is used to determine the data type of an object. It returns a type object that represents the data type of the object.

  2. How can you use the isinstance() function to check the data type of a variable?
    Answer: The isinstance() function in Python is used to determine whether an object is an instance of a specified class or not. It returns a Boolean value that indicates whether the object is an instance of the specified class or not. We can use the isinstance() function to check the data type of a variable by passing the variable and the data type we want to check it against to the function.

  3. What are type annotations in Python?
    Answer: Type annotations in Python are a feature introduced in Python 3 that allow developers to specify the data type of a variable, function parameter, or function return value using a special syntax. This helps with type checking and improving readability of the code.

  4. What is the class attribute in Python?
    Answer: The class attribute in Python is an attribute of an object that represents the class of that object. By accessing the class attribute of an object, we can determine the data type of the object.

  5. What is the inspect module used for in Python?
    Answer: The inspect module in Python provides advanced introspection capabilities. It can be used to get information about functions, classes, and methods. We can also use the inspect module to determine the data type of an object.

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Throughout my career, I have held positions ranging from Associate Software Engineer to Principal Engineer and have excelled in high-pressure environments. My passion and enthusiasm for my work drive me to get things done efficiently and effectively. I have a balanced mindset towards software development and testing, with a focus on design and underlying technologies. My experience in software development spans all aspects, including requirements gathering, design, coding, testing, and infrastructure. I specialize in developing distributed systems, web services, high-volume web applications, and ensuring scalability and availability using Amazon Web Services (EC2, ELBs, autoscaling, SimpleDB, SNS, SQS). Currently, I am focused on honing my skills in algorithms, data structures, and fast prototyping to develop and implement proof of concepts. Additionally, I possess good knowledge of analytics and have experience in implementing SiteCatalyst. As an open-source contributor, I am dedicated to contributing to the community and staying up-to-date with the latest technologies and industry trends.
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