Code 24: Falsy (& Truthy) Values

1. Python’s falsy Values

• None
• False
• 0 (integer)
• 0.0 (float)
• "" (empty string)
• [] (empty list)
• () (empty tuple)
• {} (empty dictionary)
• set() (empty set)

2. Use-Case Of falsy Values

If some variable is None, then:

• if not variable: -> Will evaluate to True

3. Empty Node: Code Example

Node and LinkedList previously introduced here.

class Node():
    def __init__(self, data):
        self.data=data
        self.next_node=None

class LinkedList():
    def __init__(self, first_node:Node|None=None):
        self.first_node: Node|None = first_node

from typing import Optional

class LinkedList_v2():
    def __init__(self, first_node: Optional[str|Node]=None):
        if isinstance(first_node,str):
            self.first_node = Node(first_node)
        elif isinstance(first_node,Node):
            self.first_node = first_node
        else:
            self.first_node = None
            
ll =  LinkedList()

print(f"LinkedList without an allocated initial Node means")
print(f"The [ll.first_node] is: \n\t{ll.first_node}") # Empty Node
print()

if not ll.first_node:
    print(f"The expression 'If not ll.first_node:' will evaluate to:")
    print(f"\t{not ll.first_node}")

LinkedList without an allocated initial Node means
The [ll.first_node] is: 
    None

The expression 'If not ll.first_node:' will evaluate to:
    True