How to Clear Variable in Python

In Python, clearing a variable means removing its value or reference. Depending on the type of variable and context, you can clear it in several ways:

1. Clearing a Variable by Reassigning None

For most types of variables, you can set their value to None to effectively clear them.

x = 42
x = None  # Clears the variable by reassigning None
print(x)  # Output: None

2. Deleting a Variable Using del

You can use the del statement to delete the variable entirely from memory. After deletion, attempting to use the variable will raise a NameError.

x = 42
del x  # Deletes the variable
# print(x)  # Raises NameError: name 'x' is not defined

3. Clearing a List, Dictionary, or Set

If the variable is a collection, you can clear its contents while keeping the variable itself intact.

• For Lists:

  my_list = [1, 2, 3]
  my_list.clear()  # Clears the list
  print(my_list)  # Output: []
  

• For Dictionaries:

  my_dict = {'a': 1, 'b': 2}
  my_dict.clear()  # Clears the dictionary
  print(my_dict)  # Output: {}
  

• For Sets:

  my_set = {1, 2, 3}
  my_set.clear()  # Clears the set
  print(my_set)  # Output: set()
  

4. Clearing a String or Numeric Variable

Strings and numeric types are immutable in Python. You can “clear” them by reassigning an empty string, 0, or another value.

• Clearing a String:

  my_string = "Hello"
  my_string = ""  # Clears the string
  print(my_string)  # Output: ''
  

• Clearing a Numeric Variable:

  my_number = 42
  my_number = 0  # Resets the number to zero
  print(my_number)  # Output: 0
  

5. Clearing All Variables (Global Scope)

If you want to clear all variables in the current session, you can use the globals() function with caution.

for key in list(globals().keys()):
    if key not in ["__builtins__", "__name__", "__doc__"]:
        del globals()[key]

This will remove all user-defined variables but keep essential system variables.

When to Use Each Method

• Use None to signify a variable is intentionally empty.
• Use del when you want to completely remove a variable.
• Use .clear() for clearing mutable collections without deleting the variable.