How do I check if a variable exists?

In Python, you can check if a variable exists by using the globals() or locals() function to check if the variable is in the global or local namespace, respectively. For example:

Check if a variable exists in the global namespace in Python

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Alternatively, you can use the globals().get() or locals().get() method to retrieve a variable's value. To safely check for existence first, use the in operator:

Check if a variable exists in the global namespace in Python by the get method

It's also possible to use the vars() function to check if a variable exists in the current namespace, which is either the global or local namespace depending on where the function is called.

Check if a variable exists in the current namespace in Python

Another way to check if a variable exists is to use the try-except block.

Check if a variable exists in Python in a try-except block

Python favors the EAFP (Easier to Ask for Forgiveness than Permission) style, so using a try-except block is generally preferred over explicit existence checks.

You can also use the hasattr() method to check if an object has a certain attribute.

Check if an object has a certain attribute in Python

Note that hasattr() checks for object attributes, not variables in the local or global namespace.