Print a variable's name in Python

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Borislav Hadzhiev

Last updated: Sep 8, 2022

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Print a variable's name in Python #

To print a variable's name:

  1. Use a formatted string literal to get the variable's name and value.
  2. Split the string on the equal sign and get the variable's name.
  3. Use the print() function to print the variable's name.
main.py
site = 'bobbyhadz.com' result = f'{site=}' print(result) # 👉️ site='bobbyhadz.com' # ✅ print variable name using f-string variable_name = f'{site=}'.split('=')[0] print(variable_name) # 👉️ 'site'

We used a formatted string literal to print a variable's name.

Formatted string literals (f-strings) let us include expressions inside of a string by prefixing the string with f.
main.py
var1 = 'bobby' var2 = 'hadz' result = f'{var1}{var2}' print(result) # 👉️ bobbyhadz

Make sure to wrap expressions in curly braces - {expression}.

Formatted string literals also enable us to use the format specification mini-language in expression blocks.

main.py
site = 'bobbyhadz.com' result = f'{site=}' print(result) # 👉️ site='bobbyhadz.com'

The equal sign after the variable is used for debugging and returns the variable's name and its value.

The expression expands to:

  1. The text before the equal sign.
  2. An equal sign.
  3. The result of calling the repr() function with the evaluated expression.

To get only the variable name, we have to split the string on the equal sign and return the first list item.

main.py
site = 'bobbyhadz.com' variable_name = f'{site=}'.split('=')[0] print(variable_name) # 👉️ 'site'

The str.split() method splits the string into a list of substrings using a delimiter.

main.py
site = 'bobbyhadz.com' result = f'{site=}' print(result) # 👉️ site='bobbyhadz.com' print(result.split('=')) # 👉️ ['site', "'bobbyhadz.com'"]

The method takes the following 2 parameters:

NameDescription
separatorSplit the string into substrings on each occurrence of the separator
maxsplitAt most maxsplit splits are done (optional)

Alternatively, you can use the globals() function.

Print a variable's name using globals() #

To print a variable's name:

  1. Use the globals() function to get a dictionary that implements the current module namespace.
  2. Iterate over the dictionary to get the matching variable's name.
  3. Use the print() function to print the variable's name.
main.py
def get_var_name(variable): globals_dict = globals() return [var_name for var_name in globals_dict if globals_dict[var_name] is variable] site = 'bobbyhadz.com' print(get_var_name(site)) # 👉️ ['site'] print(get_var_name(site)[0]) # 👉️ 'site'

The globals function returns a dictionary that implements the current module namespace.

main.py
site = 'bobbyhadz.com' globals_dict = globals() # {'site': 'bobbyhadz.com', '__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x7f235932dde0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, '__file__': '/home/borislav/Desktop/bobbyhadz_python/main.py', '__cached__': None, 'globals_dict': {...}} print(globals_dict)

We used a list comprehension to iterate over the dictionary.

main.py
site = 'bobbyhadz.com' globals_dict = globals() result = [key for key in globals_dict] # ['__name__', '__doc__', '__package__', '__loader__', '__spec__', '__annotations__', '__builtins__', '__file__', '__cached__', 'site', 'globals_dict'] print(result)
List comprehensions are used to perform some operation for every element or select a subset of elements that meet a condition.

On each iteration, we check if the identity of the provided variable matches the identity of the current dictionary value.

main.py
def get_var_name(variable): globals_dict = globals() return [var_name for var_name in globals_dict if globals_dict[var_name] is variable] site = 'bobbyhadz.com' print(get_var_name(site)) # 👉️ ['site'] print(get_var_name(site)[0]) # 👉️ 'site'

The matching variable names (keys in the dictionary) get returned as a list.

This means that if you have multiple variables with the same value, pointing to the same location in memory, the list would contain multiple variable names.

main.py
site = 'bobbyhadz.com' domain = 'bobbyhadz.com' def get_var_name(variable): globals_dict = globals() return [var_name for var_name in globals_dict if globals_dict[var_name] is variable] print(get_var_name(site)) # 👉️ ['site', 'domain']

There are 2 variables with the same value and they point to the same location in memory, so the list returns 2 variable names.

If you pass non-primitive objects to the function, you'd get a list containing only one item, because the objects are stored in different locations in memory.

main.py
class Employee(): pass alice = Employee() bobby = Employee() def get_var_name(variable): globals_dict = globals() return [var_name for var_name in globals_dict if globals_dict[var_name] is variable] print(get_var_name(alice)) # 👉️ ['alice']

The two class instances are stored in different locations in memory, so the get_var_name() function returns a list containing a single variable name.

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