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Update singly_linked_list.py (#1593)

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* Update singly_linked_list.py

printing current.data rather than node address in __repr__ for a more readable print statement

* eval(repr(c)) == c

The output of `__repr__()` _should look like a valid Python expression that could be used to recreate an object with the same value_.

https://docs.python.org/3.4/reference/datamodel.html#object.__repr__

* += --> +
This commit is contained in:
Vikas Kumar 2019-11-26 11:15:28 +05:30 committed by Christian Clauss
parent 2ad5a1f083
commit 0d3c9d586c
1 changed files with 32 additions and 44 deletions
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76
data_structures/linked_list/singly_linked_list.py
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@ -3,30 +3,30 @@ class Node: # create a Node
self.data = data # given data
self.next = None # given next to None
def __repr__(self): # String Representation of a Node
return f"<Node: {self.data}>"
def __repr__(self): # string representation of a Node
return f"Node({self.data})"
class LinkedList:
def __init__(self):
self.head = None # Initialize head to None
self.head = None # initialize head to None
def insert_tail(self, data):
def insert_tail(self, data) -> None:
if self.head is None:
self.insert_head(data) # If this is first node, call insert_head
self.insert_head(data) # if this is first node, call insert_head
else:
temp = self.head
while temp.next: # traverse to last node
temp = temp.next
temp.next = Node(data) # create node & link to tail
def insert_head(self, data):
def insert_head(self, data) -> None:
newNod = Node(data) # create a new node
if self.head:
newNod.next = self.head # link newNode to head
self.head = newNod # make NewNode as head
def printList(self): # print every node data
def print_list(self) -> None: # print every node data
temp = self.head
while temp:
print(temp.data)
@ -47,14 +47,12 @@ class LinkedList:
else:
while temp.next.next: # find the 2nd last element
temp = temp.next
temp.next, temp = (
None,
temp.next,
) # (2nd last element).next = None and temp = last element
# (2nd last element).next = None and temp = last element
temp.next, temp = None, temp.next
return temp
def isEmpty(self):
return self.head is None # Return if head is none
def is_empty(self) -> bool:
return self.head is None # return True if head is none
def reverse(self):
prev = None
@ -76,17 +74,16 @@ class LinkedList:
current = self.head
string_repr = ""
while current:
string_repr += f"{current} ---> "
string_repr += f"{current} --> "
current = current.next
# END represents end of the LinkedList
string_repr += "END"
return string_repr
return string_repr + "END"
# Indexing Support. Used to get a node at particaular position
def __getitem__(self, index):
current = self.head
# If LinkedList is Empty
# If LinkedList is empty
if current is None:
raise IndexError("The Linked List is empty")
@ -113,39 +110,30 @@ class LinkedList:
def main():
A = LinkedList()
print("Inserting 1st at head")
a1 = input()
A.insert_head(a1)
print("Inserting 2nd at head")
a2 = input()
A.insert_head(a2)
print("\nPrint List : ")
A.printList()
print("\nInserting 1st at Tail")
a3 = input()
A.insert_tail(a3)
print("Inserting 2nd at Tail")
a4 = input()
A.insert_tail(a4)
print("\nPrint List : ")
A.printList()
A.insert_head(input("Inserting 1st at head ").strip())
A.insert_head(input("Inserting 2nd at head ").strip())
print("\nPrint list:")
A.print_list()
A.insert_tail(input("\nInserting 1st at tail ").strip())
A.insert_tail(input("Inserting 2nd at tail ").strip())
print("\nPrint list:")
A.print_list()
print("\nDelete head")
A.delete_head()
print("Delete Tail")
print("Delete tail")
A.delete_tail()
print("\nPrint List : ")
A.printList()
print("\nReverse Linked List")
print("\nPrint list:")
A.print_list()
print("\nReverse linked list")
A.reverse()
print("\nPrint List : ")
A.printList()
print("\nString Representation of Linked List:")
print("\nPrint list:")
A.print_list()
print("\nString representation of linked list:")
print(A)
print("\n Reading/Changing Node Data using Indexing:")
print("\nReading/changing Node data using indexing:")
print(f"Element at Position 1: {A[1]}")
p1 = input("Enter New Value: ")
A[1] = p1
print("New List:")
A[1] = input("Enter New Value: ").strip()
print("New list:")
print(A)