Python programming Part -6

Python programming Part -6

• 1.
  Python Programming-Part 6 MeghaV Research Scholar Kannur University 15-11-2021 meghav@kannuruniv.ac.in 1
• 2.
  Difference between Methodand Function in Python Function • A function is a block of code to carry out a specific task, will contain its own scope and is called by name. • All functions may contain zero(no) arguments or more than one arguments. 15-11-2021 meghav@kannuruniv.ac.in 2
• 3.
  Difference between Methodand Function in Python Method • A method in python is somewhat similar to a function, except it is associated with object/classes. • Methods in python are very similar to functions except for two major differences. • The method is implicitly used for an object for which it is called. • The method is accessible to data that is contained within the class. 15-11-2021 meghav@kannuruniv.ac.in 3
• 4.
  List • Creating alist • Basic List operations • Indexing and slicing in Lists • Built-in functions used on lists • List methods • The del statement 15-11-2021 meghav@kannuruniv.ac.in 4
• 5.
  List • Creating alist • Lists are used to store multiple items in a single variable. thislist = ["apple", "banana", "cherry"] print(thislist) • We can update lists by using slice[] on the LHS of the assignment operator Eg: list=[‘bcd’,147,2.43,’Tom’] print(“Item at index 2=”,list[2]) list[2]=500 print(“Item at index 2=”,list[2]) Output 2.43 500 15-11-2021 meghav@kannuruniv.ac.in 5
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  List • To removean item from a list • del statement • remove() method list=[‘abcd’,147,2.43,’Tom’,74.9] print(list) del list[2] print(“list after deletion:”, list) Output [‘abcd’,147,2.43,’Tom’,74.9] list after deletion:[‘abcd’,147,’Tom’,74.9] 15-11-2021 meghav@kannuruniv.ac.in 6
• 7.
  • The delkeyword can also used to delete the list completely thislist = ["apple", "banana", "cherry"] del thislist • remove()function thislist = ["apple", "banana", "cherry"] thislist.remove("banana") print(thislist) 15-11-2021 meghav@kannuruniv.ac.in 7
• 8.
  Built-in list functions 1.len(list) – Gives the total length of list 2. max(list)- Returns item from list with maximum value 3. min(list)- Returns item from list with minimum value 4. list(seq)- Returns a tuple into a list 5. map(aFunction,aSequence) – Apply an operation to each item and collect result. 15-11-2021 meghav@kannuruniv.ac.in 8
• 9.
  Example list1=[1200,147,2.43,1.12] list2=[213,100,289] print(list1) print(list2) print(len(list1)) print(“Maximum value inlist1 is ”,max(list)) print(“Maximum value in list2 is ”,min(list)) Output [1200,147,2.43,1.12] [1200,147,2.43,1.12] 4 Maximum value in the list1 is 1200 Minimum value in the list2 is 100 15-11-2021 meghav@kannuruniv.ac.in 9
• 10.
  Example of list()and map() function tuple = (‘abcd’,147,2.43,’Tom’) print(“List:”,list(tuple)) str=input(“Enter a list(space separated):”) lis=list(map(int,str.split())) print(lis) Output List: [‘abcd’,147,2.43,’Tom’] Enter a list (space separated) : 5 6 8 9 [5,6,8,9] In this example a string is read from the keyboard and each item is converted into int using map() function 15-11-2021 meghav@kannuruniv.ac.in 10
• 11.
  Built-in list methods 1.list.append(obj) –Append an object obj passed to the existing list list = [‘abcd’,147,2.43,’Tom’] print(“Old list before append:”, list) list.append(100) print(“New list after append:”,list) Output Old list before append: [‘abcd’,147,2.43,’Tom’] New list after append: [‘abcd’,147,2.43,’Tom’,100] 15-11-2021 meghav@kannuruniv.ac.in 11
• 12.
  2. list.count(obj) –Returnshow many times the object obj appears in a list list = [‘abcd’,147,2.43,’Tom’] print(“The number of times”,147,”appears in the list=”,list.count(147)) Output The number of times 147 appears in the list = 1 15-11-2021 meghav@kannuruniv.ac.in 12
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  3. list.remove(obj) –Removes an object list1 = [‘abcd’,147,2.43,’Tom’] list.remove(‘Tom’) print(list1) Output [‘abcd’,147,2.43] 4. list.index(obj) – Returns index of the object obj if found print(list1.index(2.43)) Output 2 15-11-2021 meghav@kannuruniv.ac.in 13
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  5. list.extend(seq)- Appendsthe contents in a sequence passed to a list list1 = [‘abcd’,147,2.43,’Tom’] list2 = [‘def’,100] list1.extend(list2) print(list1) Output [‘abcd’,147,2.43,’Tom’,‘def’,100] 6. list.reverse() – Reverses objects in a list list1.reverse() print(list1) Output [‘Tom’,2.43,147,’abcd’] 15-11-2021 meghav@kannuruniv.ac.in 14
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  7. list.insert(index,obj)- Returnsa list with object obj inserted at the given index list1 = [‘abcd’,147,2.43,’Tom’] list1.insert(2,222) print(“List after insertion”,list1) Output [‘abcd’,147,222,2.43,’Tom’] 15-11-2021 meghav@kannuruniv.ac.in 15
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  8. list.sort([Key=None,Reverse=False]) –Sort the items in a list and returns the list, If a function is provided, it will compare using the function provided list1=[890,147,2.43,100] print(“List before sorting:”,list1)#[890,147,2.43,100] list1.sort() print(“List after sorting in ascending order:”,list1)#[2.43,100,147,890] list1.sort(reverse=True) print(“List after sorting in descending order:”,list1)#[890,147,100,2.43] 15-11-2021 meghav@kannuruniv.ac.in 16
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  9.list.pop([index]) – removesor returns the last object obj from a list. we can pop out any item using index list1=[‘abcd’,147,2.43,’Tom’] list1.pop(-1) print(“list after poping:”,list1) Output List after poping: [‘abcd’,147,2.43] 10. list.clear() – Removes all items from a list list1.clear() 11. list.copy() – Returns a copy of the list list2=list1.copy() 15-11-2021 meghav@kannuruniv.ac.in 17
• 18.
  Using List asStack • List can be used as stack(Last IN First OUT) • To add an item to the top of stack – append() • To retrieve an item from top –pop() stack = [10,20,30,40,50] stack.append(60) print(“stack after appending:”,stack) stack.pop() print(“Stack after poping:”,stack) Output Stack after appending:[10,20,30,40,50,60] Stack after poping:[10,20,30,40,50] 15-11-2021 meghav@kannuruniv.ac.in 18
• 19.
  Using List asQueue • List can be used as Queue data structure(FIFO) • Python provide a module called collections in which a method called deque is designed to have append and pop operations from both ends from collections import deque queue=deque([“apple”,”orange”,”pear”]) queue.append(“cherry”)#cherry added to right end queue.append(“grapes”)# grapes added to right end queue.popleft() # first element from left side is removed queu.popleft() # first element in the left side removed print(queue) Output deque([‘pear’,’cherry’,’grapes’]) 15-11-2021 meghav@kannuruniv.ac.in 19
• 20.
  LAB ASSIGNMENTS • Writea Python program to change a given string to a new string where the first and last characters have been changed • Write a Python program to read an input string from user and displays that input back in upper and lower cases • Write a program to get the largest number from the list • Write a program to display the first and last colors from a list of color values • Write a program to Implement stack operation using list • Write a program to implement queue operation using list 15-11-2021 meghav@kannuruniv.ac.in 20