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In: Computer Science

python Write a Loop class. The contents of a loop object are represented internally as a...

python

Write a Loop class. The contents of a loop object are represented internally as a simple python list with the following additional instance variables:

loop - a python list containing the elements of the loop list

head - which stores the index of the first element of the loop list

current - which stores the index of the last element of the loop list

size - which stores how many actual elements are in the loop

max - which stores the max number of elements that can be in a loop

Note that current and head will be the same when the list is empty, and when the list contains a single element.

And methods:

__init__(self, max) - which constructs an empty loop object;

__str__(self) - which returns a string representing the loop object as described below;

add(element) - which adds the element to the end of the loop (i.e. at the position of current + 1)

empty() - which says whether there are any elements in the loop;

count() - which says how many elements currently are in the loop;

delete() - which returns the first item from the loop (i.e. at the position of head) and removes it from the loop;

max() - returns the max number of elements allowed in the loop.

__init__ initializes the empty locations in the loop list to None. Assume that max is always greater than the number of elements to be in the loop at any one time. When an element is being added to an empty loop, it always goes into the first location (index 0) in the loop list and head and current are reset to 0.

If an attempt is made to delete() from an empty loop then delete() returns None. When an element is deleted from the loop its value is changed to None. Remember, your code needs to properly maintain the correct values of loop, head, current and size.

__str__ formats the loop object data as follows:

For example, after:

x = Loop(4)

x.add(1)

x.add(3)

x.delete()

print(x)

"print(x)" prints out:

4 1 1 1 [None, 3, None, None]

For example:

Test	Result
x = Loop(5) print(x)	5 0 0 0 [None, None, None, None, None]
x = Loop(5) x.add(3) print(x)	5 1 0 0 [3, None, None, None, None]
x = Loop(3) x.add(3) x.add(2) print(x)	3 2 0 1 [3, 2, None]
x = Loop(3) x.add(3) x.add(2) x.delete() print(x)	3 1 1 1 [None, 2, None]

x = Loop(3)
x.add(2)
x.add(5)
x.add(3)
x.delete()
x.add(7)
print(x)

3 3 1 0 [7, 5, 3]

Expert Solution

'''
Python version : 2.7
Python program to create and test Loop class
'''

class Loop:

   def __init__(self, max):

       self.max = max
       self.loop = [None]*max
       self.head = 0
       self.current = 0
       self.size = 0

   def __str__(self):
       return str(self.max)+" "+str(self.size)+" "+str(self.head)+" "+str(self.current)+" "+str(self.loop)

   def add(self,element):
       # if empty loop, insert in index 0
       if self.empty():
           self.loop[0] = element
           self.head = 0
           self.current = 0
           self.size += 1
       # if full loop, nothing happens
       elif self.size == self.max:
           return
       else:
           # get the next index for insertion
           self.current = (self.current + 1)%self.max
           # insert the element
           self.loop[self.current] = element
           self.size += 1 # increment the size

   def empty(self):
       return self.size == 0

   def count(self):
       return self.size

   def delete(self):
       # if loop is not empty
       if not self.empty():
           item = self.loop[self.head] # get the first element of the loop
           self.loop[self.head] = None # set the element to None
           self.size -= 1 # decrement the size
           # if loop is empty after deletion, reset head and current to 0
           if self.empty():
               self.head = 0
               self.current = 0
           else:   # update head to next element
               self.head = (self.head + 1)%self.max
           return item # return item
       return None

def max(self):
return self.max

# test the class
def main():

   x = Loop(5)
   print(x)

   x = Loop(5)
   x.add(3)
   print(x)

   x = Loop(3)
   x.add(3)
   x.add(2)
   print(x)

   x = Loop(3)
   x.add(3)
   x.add(2)
   x.delete()
   print(x)

   x = Loop(3)
   x.add(2)
   x.add(5)
   x.add(3)
   x.delete()
   x.add(7)
   print(x)

#call the main function
main()
#end of program

Code Screenshot:

Output:

venereology answered 7 months ago

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