How To Print A Variable's Name In Python

In Python, you may sometimes want to know or display the name of a variable for example, when debugging, logging, or improving code readability. Python does not provide a built-in way to retrieve a variable’s name directly, but with some clever approaches, it is possible to identify a variable by its reference in the code.

Below are several techniques to print the name of the variable:

Using locals() Function

locals() function returns a dictionary of the current local scope. By searching this dictionary, you can find which local variable references a specific value. This is useful for variables defined inside a function or the current block.

def fun(var):
    name = [k for k, v in locals().items() if v is var][0]
    print(f"Variable name using locals(): {name}")

x = 42
fun(x)

Variable name using locals(): var

Using globals() Function

The globals() function returns a dictionary of all global variables in the current module. This method is ideal for variables defined at the top level of your script or notebook.

def fun(var):
    name = [k for k, v in globals().items() if v is var][0]
    print(f"Variable name using globals(): {name}")

y = "Hello, World!"
fun(y)

Variable name using globals(): y

Using a Namespace Directly

You can search any dictionary that represents a namespace, such as locals() or globals(), to find a variable by its value. This approach is flexible and allows you to choose the scope to search in.

def fun(var, namespace):
    name = [k for k, v in namespace.items() if v is var][0]
    print(f"Variable name using namespace dict: {name}")

z = [1, 2, 3]
fun(z, locals())

Variable name using namespace dict: z

Using inspect Module

inspect module allows you to examine the calling frame, which means you can look into the local variables of the function or scope that called your code. This is the most robust method when working across different scopes.

import inspect

def fun(var):
    f1 = inspect.currentframe()
    try:
        f2 = f1.f_back.f_locals
        v1 = [name for name, value in f2.items() if value is var][0]
        print(f"Variable name: {v1}")
    finally:
        del f1  

var = 42
fun(var)

Variable name: var

Related Articles:

• Global and Local Variables in Python
• Inspect Module in Python