Python locals() Function

The locals() function in Python returns a dictionary representing the current local symbol table. This means it gives you a snapshot of all local variables and their values at a particular point in your code.

Syntax

locals()

Parameters:

• None – This function takes no arguments.

Returns:

• A dict object containing all local variables in the current scope.

Example 1: Using locals() in a Function

def show_locals():
    a = 10
    b = "Hello"
    print(locals())

show_locals()

{'a': 10, 'b': 'Hello'}

Example 2: Using locals() in the Global Scope

x = 5
y = 7
print(locals())

Output (in interactive mode):

{'x': 5, 'y': 7, ...}

In a script, locals() at the global level behaves like globals().

Use Case: Debugging and Dynamic Variable Handling

• Helpful during debugging to inspect current variable states.
• Used in advanced applications like dynamic form builders or interpreters.
• Can be passed to eval() or exec() to evaluate expressions in the current local context.

Modifying the Returned Dictionary

While you can modify the dictionary returned by locals(), these changes may not affect actual local variables (especially inside functions).

Example:

def test():
    x = 1
    loc = locals()
    loc['x'] = 99
    print("x =", x)

test()

x = 1

Why? Because changes to the dictionary don’t always reflect back in the local scope.

Common Mistakes

• Assuming modifying locals() will update variables – it might not.
• Using locals() for simple scripts unnecessarily can confuse beginners.

Interview Tip

Interviewers might ask about the difference between locals() and globals(). Remember: locals() gives variables in the current function or scope, while globals() gives variables at the module level.

Summary

• locals() returns a dictionary of current local variables.
• Used for debugging, dynamic evaluation, and introspection.
• Modifying the dictionary might not change actual variables inside a function.

Practice Problem

Write a function where you declare 3 variables, print them, and also print locals(). Observe the difference.

def demo():
    a = 1
    b = 2
    c = a + b
    print("Sum is:", c)
    print("Local variables:", locals())

demo()