Simplify code by dropping support for legacy Python

CONTRIBUTING.md

@@ -56,7 +56,7 @@ We want your work to be readable by others; therefore, we encourage you to note
 
   ```python
       """
-  	This function sums a and b    
+  	This function sums a and b
   """
   def sum(a, b):
       return a + b
@@ -82,13 +82,13 @@ We want your work to be readable by others; therefore, we encourage you to note
   The following "testing" approaches are **not** encouraged:
 
   ```python
-  input('Enter your input:') 
+  input('Enter your input:')
   # Or even worse...
-  input = eval(raw_input("Enter your input: "))
+  input = eval(input("Enter your input: "))
   ```
-  
+
   However, if your code uses __input()__ then we encourage you to gracefully deal with leading and trailing whitespace in user input by adding __.strip()__ to the end as in:
-  
+
   ```python
   starting_value = int(input("Please enter a starting value: ").strip())
   ```
@@ -99,13 +99,13 @@ We want your work to be readable by others; therefore, we encourage you to note
   def sumab(a, b):
       return a + b
   # Write tests this way:
-  print(sumab(1,2))	# 1+2 = 3
-  print(sumab(6,4))	# 6+4 = 10
+  print(sumab(1, 2))	# 1+2 = 3
+  print(sumab(6, 4))	# 6+4 = 10
   # Or this way:
-  print("1 + 2 = ", sumab(1,2))	# 1+2 = 3
-  print("6 + 4 = ", sumab(6,4))	# 6+4 = 10
+  print("1 + 2 = ", sumab(1, 2))	# 1+2 = 3
+  print("6 + 4 = ", sumab(6, 4))	# 6+4 = 10
   ```
-  
+
   Better yet, if you know how to write [__doctests__](https://docs.python.org/3/library/doctest.html), please consider adding them.
 
 - Avoid importing external libraries for basic algorithms. Only use those libraries for complicated algorithms.

ciphers/affine_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import sys, random, cryptomath_module as cryptoMath
 
 SYMBOLS = r""" !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"""

ciphers/atbash.py

@@ -1,23 +1,15 @@
-try:               # Python 2
-    raw_input
-    unichr
-except NameError:  # Python 3
-    raw_input = input
-    unichr = chr
-
-
-def Atbash():
+def atbash():
     output=""
-    for i in raw_input("Enter the sentence to be encrypted ").strip():
+    for i in input("Enter the sentence to be encrypted ").strip():
         extract = ord(i)
         if 65 <= extract <= 90:
-            output += unichr(155-extract)
+            output += chr(155-extract)
         elif 97 <= extract <= 122:
-            output += unichr(219-extract)
+            output += chr(219-extract)
         else:
-            output+=i
+            output += i
     print(output)
 
 
 if __name__ == '__main__':
-    Atbash()
+    atbash()

ciphers/brute_force_caesar_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 def decrypt(message):
     """
     >>> decrypt('TMDETUX PMDVU')

ciphers/onepad_cipher.py

@@ -1,5 +1,3 @@
-from __future__ import print_function
-
 import random
 
 
@@ -15,7 +13,7 @@ def encrypt(self, text):
             cipher.append(c)
             key.append(k)
         return cipher, key
-    
+
     def decrypt(self, cipher, key):
         '''Function to decrypt text using psedo-random numbers.'''
         plain = []

ciphers/rabin_miller.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 # Primality Testing with the Rabin-Miller Algorithm
 
 import random

ciphers/rot13.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 def dencrypt(s, n):
     out = ''
     for c in s:

ciphers/rsa_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import sys, rsa_key_generator as rkg, os
 
 DEFAULT_BLOCK_SIZE = 128
@@ -16,7 +15,7 @@ def main():
     if mode == 'encrypt':
         if not os.path.exists('rsa_pubkey.txt'):
             rkg.makeKeyFiles('rsa', 1024)
-            
+
         message = input('\nEnter message: ')
         pubKeyFilename = 'rsa_pubkey.txt'
         print('Encrypting and writing to %s...' % (filename))

ciphers/rsa_key_generator.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import random, sys, os
 import rabin_miller as rabinMiller, cryptomath_module as cryptoMath
 

ciphers/simple_substitution_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import sys, random
 
 LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
@@ -18,7 +17,7 @@ def main():
         translated = decryptMessage(key, message)
 
     print('\n%sion: \n%s' % (mode.title(), translated))
-    
+
 def checkValidKey(key):
     keyList = list(key)
     lettersList = list(LETTERS)
@@ -49,7 +48,7 @@ def translateMessage(key, message, mode):
 
     if mode == 'decrypt':
         charsA, charsB = charsB, charsA
-        
+
     for symbol in message:
         if symbol.upper() in charsA:
             symIndex = charsA.find(symbol.upper())

ciphers/transposition_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import math
 
 def main():

ciphers/transposition_cipher_encrypt_decrypt_file.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import time, os, sys
 import transposition_cipher as transCipher
 
@@ -16,7 +15,7 @@ def main():
         response = input('> ')
         if not response.lower().startswith('y'):
             sys.exit()
-            
+
     startTime = time.time()
     if mode.lower().startswith('e'):
         with open(inputFile) as f:
@@ -29,9 +28,9 @@ def main():
 
     with open(outputFile, 'w') as outputObj:
         outputObj.write(translated)
-    
+
     totalTime = round(time.time() - startTime, 2)
     print(('Done (', totalTime, 'seconds )'))
-    
+
 if __name__ == '__main__':
     main()

ciphers/vigenere_cipher.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
 
 def main():

data_structures/binary_tree/binary_search_tree.py

@@ -1,7 +1,6 @@
 '''
 A binary search Tree
 '''
-from __future__ import print_function
 class Node:
 
     def __init__(self, label, parent):
@@ -66,8 +65,8 @@ def insert(self, label):
             else:
                 parent_node.setRight(new_node)
             #Set parent to the new node
-            new_node.setParent(parent_node)      
-    
+            new_node.setParent(parent_node)
+
     def delete(self, label):
         if (not self.empty()):
             #Look for the node with that label
@@ -92,7 +91,7 @@ def delete(self, label):
                     self.delete(tmpNode.getLabel())
                     #Assigns the value to the node to delete and keesp tree structure
                     node.setLabel(tmpNode.getLabel())
-    
+
     def getNode(self, label):
         curr_node = None
         #If the tree is not empty
@@ -177,7 +176,7 @@ def traversalTree(self, traversalFunction = None, root = None):
             #Returns a list of nodes in the order that the users wants to
             return traversalFunction(self.root)
 
-    #Returns an string of all the nodes labels in the list 
+    #Returns an string of all the nodes labels in the list
     #In Order Traversal
     def __str__(self):
         list = self.__InOrderTraversal(self.root)
@@ -203,7 +202,7 @@ def testBinarySearchTree():
                / \    \
               1   6    14
                  / \   /
-                4   7 13 
+                4   7 13
     '''
 
     r'''
@@ -236,11 +235,11 @@ def testBinarySearchTree():
         print("The label -1 exists")
     else:
         print("The label -1 doesn't exist")
-    
+
     if(not t.empty()):
         print(("Max Value: ", t.getMax().getLabel()))
         print(("Min Value: ", t.getMin().getLabel()))
-    
+
     t.delete(13)
     t.delete(10)
     t.delete(8)

data_structures/binary_tree/fenwick_tree.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 class FenwickTree:
 
     def __init__(self, SIZE): # create fenwick tree with size SIZE

data_structures/binary_tree/lazy_segment_tree.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import math
 
 class SegmentTree:

data_structures/binary_tree/segment_tree.py

@@ -1,4 +1,3 @@
-from __future__ import print_function
 import math
 
 class SegmentTree:

data_structures/heap/heap.py

@@ -1,15 +1,8 @@
 #!/usr/bin/python
 
-from __future__ import print_function, division
-
-try:
-    raw_input          # Python 2
-except NameError:
-    raw_input = input  # Python 3
-
-#This heap class start from here.
+# This heap class start from here.
 class Heap:
-	def __init__(self): #Default constructor of heap class.
+	def __init__(self): # Default constructor of heap class.
 	    self.h = []
 	    self.currsize = 0
 
@@ -79,7 +72,7 @@ def display(self): #This function is used to print the heap.
 		print(self.h)
 
 def main():
-	l = list(map(int, raw_input().split()))
+	l = list(map(int, input().split()))
 	h = Heap()
 	h.buildHeap(l)
 	h.heapSort()

data_structures/linked_list/doubly_linked_list.py

@@ -4,14 +4,13 @@
 - Each link references the next link and the previous one.
 - A Doubly Linked List (DLL) contains an extra pointer, typically called previous pointer, together with next pointer and data which are there in singly linked list.
  - Advantages over SLL - IT can be traversed in both forward and backward direction.,Delete operation is more efficent'''
-from __future__ import print_function
 
 
 class LinkedList:           #making main class named linked list
     def __init__(self):
         self.head = None
         self.tail = None
-        
+
     def insertHead(self, x):
         newLink = Link(x)                            #Create a new link with a value attached to it
         if(self.isEmpty() == True):                  #Set the first element added to be the tail
@@ -20,52 +19,52 @@ def insertHead(self, x):
             self.head.previous = newLink             # newLink <-- currenthead(head)
         newLink.next = self.head                     # newLink <--> currenthead(head)
         self.head = newLink                          # newLink(head) <--> oldhead
-    
+
     def deleteHead(self):
         temp = self.head
-        self.head = self.head.next                   # oldHead <--> 2ndElement(head) 
+        self.head = self.head.next                   # oldHead <--> 2ndElement(head)
         self.head.previous = None                    # oldHead --> 2ndElement(head) nothing pointing at it so the old head will be removed
         if(self.head is None):
             self.tail = None                         #if empty linked list
         return temp
-    
+
     def insertTail(self, x):
         newLink = Link(x)
         newLink.next = None                         # currentTail(tail)    newLink -->
         self.tail.next = newLink                    # currentTail(tail) --> newLink -->
         newLink.previous = self.tail                #currentTail(tail) <--> newLink -->
         self.tail = newLink                         # oldTail <--> newLink(tail) -->
-    
+
     def deleteTail(self):
         temp = self.tail
         self.tail = self.tail.previous              # 2ndLast(tail) <--> oldTail --> None
         self.tail.next = None                       # 2ndlast(tail) --> None
         return temp
-    
+
     def delete(self, x):
         current = self.head
-        
+
         while(current.value != x):                  # Find the position to delete
             current = current.next
-            
+
         if(current == self.head):
             self.deleteHead()
-            
+
         elif(current == self.tail):
             self.deleteTail()
-            
+
         else: #Before: 1 <--> 2(current) <--> 3
             current.previous.next = current.next # 1 --> 3
             current.next.previous = current.previous # 1 <--> 3
-    
+
     def isEmpty(self):                               #Will return True if the list is empty
         return(self.head is None)
-        
+
     def display(self):                                #Prints contents of the list
         current = self.head
         while(current != None):
             current.displayLink()
-            current = current.next  
+            current = current.next
         print()
 
 class Link: