How to Check If Variable Exists in Python

Here are four methods to check if a variable exists in Python.

1. Using “locals()” function
2. Using “globals()” function
3. Using “in operator”
4. Using the “try/except” method

Method 1: Python locals()

The locals() is a built-in Python function that returns a “dictionary” of the current local symbol table. The local symbol table stores all information needed for the local scope of the program, and this information is accessed using the built-in function locals().

kb = 19
kl = 21

print(locals())

Output

{'__name__': '__main__', '__doc__': None, '__package__': None, 
 '__loader__': <_frozen_importlib_external.SourceFileLoader object at 0x102c0cca0>,
 '__spec__': None, '__annotations__': {}, '__builtins__': <module 'builtins' (built-in)>, 
 '__file__': '/Users/krunallathiya/Desktop/Code/Python/app.py', '__cached__': None, 
 'kb': 19, 'kl': 21}

Method 2: Python globals()

The globals() is a built-in Python function that returns the dictionary of the current global symbol table. The symbol table contains all the program’s essential information, including classes, methods, and variable names.

kb = 19
kl = 21


def add():
 mbb = 11
 ans = mbb + kb

 globals()['kb'] = ans
 print(ans)


add()

Output

30

Method 3: Python in operator

To check if a variable exists in Python, you can use the “in operator” and check inside the “locals()” dictionary.

To check if a global variable exists, you can use the “in operator” and check inside the “globals()” dictionary.

if 'main_var' in locals():
  print('Variable exists')
else:
  print('Variable does not exist')

Output

Variable does not exist

Method 4: Using try and except block

try:
 main_var
 print("Variable exists")
except NameError:
 print("Error: No value detected")

Output

Error: No value detected

That’s it.

Krunal

Krunal Lathiya is a seasoned Computer Science expert with over eight years in the tech industry. He boasts deep knowledge in Data Science and Machine Learning. Versed in Python, JavaScript, PHP, R, and Golang. Skilled in frameworks like Angular and React and platforms such as Node.js. His expertise spans both front-end and back-end development. His proficiency in the Python language stands as a testament to his versatility and commitment to the craft.