How to check if a variable is a dictionary in Python?

Question

Jayant Kumar · Accepted Answer

Table of Contents
Introduction
In Python, you must check the type of a variable to ensure you’re using it correctly in your code. A common task is determining whether a variable is a dictionary. Since a dictionary in Python is a collection of key-value pairs, it’s important to verify this before performing any dictionary-specific operations. This guide explores various methods to check if a variable is a dictionary in Python.
How to Check if a Variable is a Dictionary
Method 1: Using isinstance() 
The isinstance() function is a simple and Pythonic way to check if a variable is a dictionary. It requires two arguments: the variable you want to check and the type you’re checking for (in this case, dict). This method is recommended because it’s both readable and flexible.
Example:
# Sample variables
my_dict = {'name': 'Alice', 'age': 25}
my_list = ['apple', 'banana', 'cherry']

# Checking if my_dict is a dictionary
if isinstance(my_dict, dict):
    print("my_dict is a dictionary.")
else:
    print("my_dict is not a dictionary.")

# Output: my_dict is a dictionary.

# Checking if my_list is a dictionary
if isinstance(my_list, dict):
    print("my_list is a dictionary.")
else:
    print("my_list is not a dictionary.")

# Output: my_list is not a dictionary.

Method 2: Using type() 
The type() function returns the data type of the variable you pass to it. You can use this function to verify if a variable is of type dict. While this method directly checks the type, it’s less flexible than isinstance() because it doesn’t account for inheritance.
Example:
# Sample variables
my_dict = {'name': 'Alice', 'age': 25}
my_list = ['apple', 'banana', 'cherry']

# Checking if my_dict is a dictionary
if type(my_dict) == dict:
    print("my_dict is a dictionary.")
else:
    print("my_dict is not a dictionary.")

# Output: my_dict is a dictionary.

# Checking if my_list is a dictionary
if type(my_list) == dict:
    print("my_list is a dictionary.")
else:
    print("my_list is not a dictionary.")

# Output: my_list is not a dictionary.

Method 3: Using Duck Typing with try-except
Python’s dynamic typing allows you to use duck typing to check if a variable behaves like a dictionary. This involves performing a dictionary-specific operation, such as accessing a key, within a try-except block. If a TypeError or AttributeError occurs, the variable is not a dictionary.
Example:
# Sample variables
my_dict = {'name': 'Alice', 'age': 25}
my_list = ['apple', 'banana', 'cherry']

# Checking if my_dict behaves like a dictionary
try:
    _ = my_dict['name']
    print("my_dict is a dictionary.")
except (TypeError, AttributeError):
    print("my_dict is not a dictionary.")

# Output: my_dict is a dictionary.

# Checking if my_list behaves like a dictionary
try:
    _ = my_list['name']
    print("my_list is a dictionary.")
except (TypeError, AttributeError):
    print("my_list is not a dictionary.")

# Output: my_list is not a dictionary.

Practical Examples
Example 1: Validate Input Data Type
You may need to check if an input is a dictionary before processing it further in a function.
def process_data(data):
    if not isinstance(data, dict):  # Python isinstance dict
        raise ValueError("Expected a dictionary as input.")
    # Proceed with processing if data is a dictionary
    print("Processing dictionary data...")

# Valid input
input_data = {'key': 'value'}
process_data(input_data)  # Output: Processing dictionary data...

# Invalid input
input_data = [1, 2, 3]
process_data(input_data)  # Raises ValueError: Expected a dictionary as input.

Example 2: Handling Configuration Settings
When reading configuration settings from a file or environment, ensure that the settings are stored as a dictionary.
def load_config(config):
    if isinstance(config, dict):  # Python check if variable is dictionary
        print("Configuration loaded successfully.")
    else:
        print("Invalid configuration format. Please provide a dictionary.")

# Valid configuration
config_settings = {'host': 'localhost', 'port': 8080}
load_config(config_settings)  # Output: Configuration loaded successfully.

# Invalid configuration
config_settings = 'host=localhost;port=8080'
load_config(config_settings)  # Output: Invalid configuration format. Please provide a dictionary.

Conclusion
You can check if a variable is a dictionary in Python using isinstance(), type(), or duck typing with try-except. Generally, isinstance() is the best option because of its clarity and flexibility. Understanding how to check a variable’s type helps you write reliable and error-free code, especially when dealing with various data types.

How to check if a variable is a dictionary in Python?

Table of Contents

Introduction

How to Check if a Variable is a Dictionary

Method 1: Using `isinstance()`

Method 2: Using `type()`

Method 3: Using Duck Typing with `try-except`

Practical Examples

Example 1: Validate Input Data Type

Conclusion

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