How to check if type of a variable is string in Python?

In Python, it is essential to verify the type of a variable before performing operations on it. For example, if you want to use string methods like upper() or lower(), you need to ensure the variable is actually a string to avoid errors.

Python provides several ways to check if a variable is of type string. Let's explore the most common approaches.

Using isinstance() Function

The isinstance() function is the recommended approach to check variable types in Python. It takes two arguments: the variable to check and the type to check against, returning True if the variable matches the specified type.

Syntax

isinstance(object, type)

Example 1: String Variable

Here's how to check if a variable contains a string ?

text = "Tutorialspoint"
print("Checking if the variable is a string:")
print(isinstance(text, str))
print(f"Type: {type(text).__name__}")

Checking if the variable is a string:
True
Type: str

Example 2: Non-String Variable

Let's test with a non-string variable ?

number = 42
print("Checking if the variable is a string:")
print(isinstance(number, str))
print(f"Type: {type(number).__name__}")

Checking if the variable is a string:
False
Type: int

Using type() Function

The type() function returns the exact type of a variable. You can compare it directly with the str class using the equality operator.

Syntax

type(object)

Example

Here's how to use type() for string checking ?

variables = ["Welcome", 123, 45.67, True]

for var in variables:
    if type(var) == str:
        print(f"'{var}' is a string")
    else:
        print(f"'{var}' is {type(var).__name__}, not a string")

'Welcome' is a string
'123' is int, not a string
'45.67' is float, not a string
'True' is bool, not a string

Comparison of Methods

Practical Example

Here's a practical function that safely processes string variables ?

def process_text(data):
    if isinstance(data, str):
        return data.upper().strip()
    else:
        return f"Error: Expected string, got {type(data).__name__}"

# Test with different data types
test_values = ["  hello world  ", 123, None, "Python"]

for value in test_values:
    result = process_text(value)
    print(f"Input: {value} ? Output: {result}")

Input:   hello world   ? Output: HELLO WORLD
Input: 123 ? Output: Error: Expected string, got int
Input: None ? Output: Error: Expected string, got NoneType
Input: Python ? Output: PYTHON

Conclusion

Use isinstance(variable, str) for checking string types as it's the recommended approach in Python. The type() method works but doesn't handle inheritance properly. Always validate variable types before performing type-specific operations to prevent runtime errors.