How can Python detect if a variable is set?

In Python, you can use the globals() function to check if a variable is set. This function returns a dictionary containing the current global variables and their values. You can use the in operator to check if a variable is in this dictionary. Here is a simple example:

# 检查变量是否设置
if 'my_variable' in globals():
    print("my_variable已设置")
else:
    print("my_variable未设置")

Additionally, you can use the locals() function to check if local variables have been set. This function returns a dictionary containing the current local variables and their values, similar to how globals() works.