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Python - del and None

📌 What You Will Learn
  • Define the del keyword and the None value
  • Delete variables with the del keyword
  • Understand the NameError raised when accessing a deleted variable
  • Explain why deleting an element of a string raises a TypeError
  • Distinguish the unbind operation of del from the rebind operation of assigning None

Introduction

Python provides the del keyword to delete variables.

Python also provides the special value None, which represents "no value".

Although both are related to object management, they work differently.

del Statement

del is a keyword in Python.

After using a variable, it is recommended to delete it if it is no longer required.

After deleting the variable, the corresponding object becomes eligible for Garbage Collection (if no other references exist).

Syntax

🐍Code Cell
1del variable_name
Output
No output captured.

Example 1 - Delete a Variable

🐍Code Cell
1x = 10
2 
3print(x)
4 
5del x
Output
10

Example 2 - Accessing a Deleted Variable

After deleting a variable, it cannot be accessed.

If we try to access it, Python raises a NameError.

Program

🐍Code Cell
1x = 10
2 
3del x
4 
5print(x)
Output
NameError: name 'x' is not defined

Important Note

We can delete variables that point to immutable objects.

However, we cannot delete individual elements of an immutable object.

Example - Immutable Object

🐍Code Cell
1s = "durga"
2 
3print(s)
4 
5del s[0] # Invalid
Output
durga

TypeError: 'str' object doesn't support item deletion

Why Does This Error Occur?

A string is an immutable object.

Immutable objects cannot be modified after creation.

Therefore, deleting an individual character from a string is not allowed.

Difference Between del and None

Both del and None are used while working with variables, but their behavior is different.

Case 1 - Using del

  • The variable is removed.
  • The variable cannot be accessed afterwards.
  • It is called an Unbind Operation.

Example - Using del

🐍Code Cell
1s = "durga"
2 
3del s
4 
5print(s)
Output
NameError: name 's' is not defined

Case 2 - Assigning None

  • The variable is not removed.
  • The previous object becomes eligible for Garbage Collection (if no other references exist).
  • The variable still exists.
  • It is called a Rebind Operation.

Example - Assign None

🐍Code Cell
1s = "durga"
2 
3s = None
4 
5print(s)
Output
None

Explanation

After assigning None, the variable still exists.

Its value becomes None.

Therefore, it can still be accessed.

Comparison Between del and None

del None
Removes the variable. Does not remove the variable.
Variable cannot be accessed. Variable can still be accessed.
Unbind operation. Rebind operation.
Raises NameError when accessed. Prints None.
Object becomes eligible for Garbage Collection. Previous object becomes eligible for Garbage Collection.

Real World Usage

The del keyword and None are commonly used in:

  • Memory management
  • Large applications
  • Object cleanup
  • Resetting variable values
  • Garbage collection optimization
📝 Key Takeaways
  • del is a Python keyword used to delete variables
  • Accessing a deleted variable raises a NameError
  • Individual elements of immutable objects like strings cannot be deleted
  • Deleting a variable is called an unbind operation
  • Assigning None is called a rebind operation and the variable still exists

🧠 Test Your Knowledge

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