How to print a variable's name in Python

Python doesn’t provide a function to print a variable’s name, so you need to use a custom solution if you want to print the name of a variable.

There are 3 different ways you can print a variable’s name in Python:

1. Using the f-string format and split() method
2. Using the globals() function
3. Using the locals() function

This tutorial will show you how to use the above methods in practice.

1. Use the f-string format

In Python version 3.8, the f-string format can now be used to print a variable’s name and value by adding the assignment = operator after the variable’s name.

Consider this example:

name = "Nathan"

print(f"{name=}")

Output:

name='Nathan'

Knowing this feature, you can use the split() method and get the first item in the resulting list to get a variable’s name.

Here’s an example:

name = "Nathan"

print(f"{name=}".split('=')[0])

Output:

name

The .split('=') method will split the string returned by the f-string format, so you get a list of two items: the name of the variable and the value.

From there, you only need to get the variable name using the subscript notation [0].

And that’s how you can print a variable’s name in Python. Note that this solution only works for Python version 3.8+, so you need to use the other solutions if you need to support older Python versions.

2. Use the globals() function

The Python globals() function is used to get a dictionary containing the current scope’s global variables.

To show you how the globals() function work, run the following code:

first_variable = "A"
my_pet = "Leo"

global_dict = globals()

print(global_dict)

You should see the two variables first_variable and my_pet listed in the global_dict object as follows:

{
    '__cached__': None,
    'first_variable': 'A',
    'my_pet': 'Leo',
    'global_dict': {...}
}

Knowing this, you can return the key of the item that has the same value as the variable.

You can use a list comprehension to iterate over the global dictionary as follows:

first_variable = "A"

global_dict = globals()

the_name = [name for name in global_dict if global_dict[name] == first_variable]

print(the_name)

Output:

['first_variable']

Since a list comprehension returns a list, you need to add the subscript notation [0] if you want the variable name as a string object.

Note that if you use a for loop to replace list comprehension, Python will raise the RuntimeError: dictionary changed size during iteration.

I’m not sure why, but it seems the for loop add something to the global dictionary object.

If you want to use a for loop, you need to copy the dictionary as follows:

first_variable = "A"

global_dict = globals()

for key, value in global_dict.copy().items():
    if value == first_variable:
        print(key)

But I suggest you create a custom function to get the variable name as follows:

def get_name(x):
    global_dict = globals()
    for key, value in global_dict.items():
        if value == x:
            return key


first_variable = "A"
my_pet = "Leo"

print(get_name(first_variable))
print(get_name(my_pet))

Output:

first_variable
my_pet

When you call the globals() function inside a function, iterating over the dictionary object doesn’t raise the RuntimeError.

Use the locals() function

Python also has the locals() function, which is used to create a dictionary containing the current scope’s local variables.

You can use the locals() function to get a variable’s name as follows:

first_variable = "A"

local_dict = locals()

for key, value in local_dict.copy().items():
    if value == first_variable:
        print(key)

The locals() function works in a similar manner to the globals() function, but you can’t create a custom function to get a variable’s name using locals().

This is because the local scope inside the function won’t store the reference to the variable outside of it. If you run the following code:

def get_name(x):
    local_dict = locals()
    for key, value in local_dict.items():
        if value == x:
            return key


first_variable = "A"
my_pet = "Leo"

print(get_name(first_variable))
print(get_name(my_pet))

Output:

x
x

As you can see, the get_name() function returns the parameter name instead of the actual variable name.

You need to use the globals() function when creating a custom function to extract variable names.

Conclusion

Usually, you don’t need to print a variable name when developing a Python program.

But you might need to do this when you encounter a bug in your program, so you need to create a workaround since Python doesn’t provide a property that returns the variable name.

In the latest version of Python, you can use the f-string format and split() method to get the variable name.

If you need to support older Python versions, I recommend you create a custom function using the globals() function as shown in this tutorial.

I hope this tutorial has been useful. Happy coding and see you another time! 👋