lab7-kgashok.py

Table of Contents

Lab 7: Removing all the duplicate elements in a list

[TOC]

Problem statement

Write a python program that removes all the duplicate elements in a list.

Sample Input0: [1, 2, 3, 4]
Sample Output0: [1, 2, 3, 4]

Sample Input1: [1, 2, 3, 4, 4]
Sample Output1: [1, 2, 3]

Sample Input2: [5, 5, 5, 5]
Sample Output2: []

Sample Input3: [11, 22, 33, 44, 22]
Sample Output3: [11, 33, 44]

Solution Key

#!/usr/bin/python
# -*- coding: utf-8 -*-


def remove_duplicates(mlist):
    tokens = {}
    for elem in mlist:
        tokens[elem] = 1

    return list(tokens.keys())


def get_list_of_elements():
    """returns a list containing elements entered by user
....The sequence of steps in the algorithm is:
....#1 - initialize the list
....#2 - Start loop for maximum of 10 entries
........#3 - Get input from user. If null, break
........#4 - Append the element to the list
....#5 - Return the list containing elements
...."""

    ilist = []  # 1
    for x in range(0, 10):  # 2
        element = input('Enter element ' + str(x) + ': ')
        if element:
            ilist.append(element)  # 4
        else:
            break  # 3
    return ilist  # 5


# Program starts here

elist = get_list_of_elements()
print ('List of elements: ', elist)
nlist = remove_duplicates(elist)
print ('The list after removing duplicates ', nlist)

CloudCoder Exercise

TBD

Pre-Lab Questions

  1. If a list contains [1, 2, 3, 'python', 3, 4, 'python1', 'python', 5], what would the list look like after all the duplicates are removed?

  2. If a list contains [5, 5, 5, 5, 5, 6, [1, 2, 6], [1, 2, 6]], what would the list contain after all the duplicates are removed?

  3. What is the method available to remove an element from a list?

  4. How will you get a list of all the keys that are present in a dictionary (which basically contains a key:value pair)?

  5. How will get a list of all the values that are present in a dictionary?

  6. What is the python code for building a dictionary out of 3 tuples? For e.g.

    ("jan", 31) ("feb", 28) and ("mar", 31) `

  7. What is the value of L after you run the code below?

Post-Lab Questions

  1. Rewrite the code to use only lists and not a dictionary. Or vice versa. Provide analysis to whether the eventual output is stable or unstable.

  2. You are not allowed to use another data structure to remove duplicates. That is, remove the duplicates in-place. Is this possible?

  3. How will you find the common elements that exist in two different lists?

  4. Write a program to calculate the product of all the integers that are available in a list. For e.g. if alist = [2, 3, 5, 8], then product(alist) = 240

  5. Find the gcd of two integers using the prime factorization method. Review video at http://j.mp/whatIsPrime and http://j.mp/gcdPrime. Use the function you developed in Lab 5 to complete this. Here's an outline for the function that you will need to develop:

    def gcd(n1, n2):
    prime_factors_of_n1 = prime_factors(n1)
    prime_factors_of_n2 = prime_factors(n2)
    common_prime_factors = \
        intersect_list(prime_factors_of_n1, prime_factors_of_n2)

    product_of_common_prime_factors = product(common_prime_factors)
    return product_of_common_prime_factors

Bonus 1

  1. You are asked to remove all the duplicate occurrences of only one specific element in the list. Write a function for this.

  2. Count the number of number of distinct characters that occur more than once in the string. Read the problem statement and solve on CC - http://j.mp/countDuplicates

  3. Write a program that will analyze whether a string is an isogram, pangram or a partial perfect pangram. Also if the string contains duplicates, count the number of duplicate characters that are there in the string.

    • And how about checking whether two words are their respective anagrams? And if not, how many changes are needed to make them?

Bonus 2

  1. There is probably a one-line Pythonic solution for almost every complicated problem out there. That is also the case for this lab exercise. Can you figure it out?

  2. There is even a shorter one liner if you use another powerful Python data type. Can you figure it out?

  3. Between 1 and 2, which solution is more preferable? And why?

Interview grade

Calculate the gcd for a list of integers using the prime factorization method. The method is well described in the video at http://j.mp/gcdPrime - use lists as part of the solution.

Related Links

https://goo.gl/v7ephq http://j.mp/removeDuplicates

Predict the output of Snippet1

mylist = [1, 5, 1, 2, 3, 4, 2, 7, 4, 6]
if mylist:
    mylist.sort()
    last = mylist[-1]
    for i in range(len(mylist)-2, -1, -1):
      if last == mylist[i]:
          del mylist[i]
      else:
          last = mylist[i]

print(mylist)

Predict the output of Snippet2

u = [1, 5, 1, 2, 3, 4, 2, 7, 4, 6]
for x in s:
    if x not in u:
        u.append(x)
print (u)

Analyze Snippet1 vs Snippet2

  1. Both mylist and u are identical lists. True or False?

  2. At the end of execution of their respective codes, mylist from Snippet1 and u from Snippet2 will always be of the same size, as long as they both start off by being equal. True or False?

  3. At the end of execution of their respective codes, mylist and u will have the same contents, in the same order. True or False?

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