Introduction to python

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Introduction to python

  1. 1. Introduction To Python Basics, sequences, Dictionaries, Sets
  2. 2. Python – Python is an interepted language, which can save you considerable time during program development because no compilation and linking is necessary.
  3. 3. How to install Python • Download latest version of python and install it on any drive: say D:python • Then follow the steps –Got to Control Panel -> System -> Advanced system settings –Click the Environment variables... button –Edit PATH and append ;d:Python to the end –Click OK. –Open command prompt type python and enter
  4. 4. C Vs Python Syntax comparison
  5. 5. Commenting // comment single line /* comment multiple lines */ # comment single line “ ” ” comment multiple lines “ ” ” C Python
  6. 6. Variables //Declaring a variable Int a=10; Char c=‘a’; Float f=1.12; //Cannot assign multiple values a=b=4 // Will result error #No need of prior Declarations a=10 c=‘a’ f=1.12 #Can assign multiple values simultaneously x = y = z = 10 a, b, c = 1, 2, "john" C Python
  7. 7. OutPut printf(“Hello baabtra”); Int a=10,b=25; Printf(“%d %d”,a,b); Printf(“value of a=%d and b= %d”,a,b) print(“Hello baabtra”) a=10 b=25 print(a,b) print (“value of a=%d and b= %d” % (a,b)) C Python
  8. 8. InPut int a; Printf(“Enter the number”); scanf(“%d”,&a); a=input(“Enter the number”) C Python
  9. 9. Arrays int a[]={12,14,15,65,34}; printf(“%d”, a[3]); No Arrays ! Instead Lists a = [12,14,15,16,65,34,’baabtra’] C Python
  10. 10. Arrays int a[]={12,14,15,65,34}; printf(“%d”, a[3]); No Arrays ! Instead Lists a = [12,14,15,16,65,34,’baabtra’] C Python [ 12 , 14 , 15 , 16 , 65 , 34 , ’baabtra’ ] 0 1 2 3 4 5 6 -7 -6 -5 -4 -3 -2 -1
  11. 11. Lists in detail • Print(a[2:5]) # prints 15,16,65 • Print(a[-6:-2]) # prints 14,15,16,65 • Print(a[4:]) # prints 65,34,baabtra • Print(a[:2]) # prints 12,14,15 • a[2] = a[2] + 23; # Lists are mutable,we can change individual items • a[0:2] = [1, 12] # We can replace a group of items together • a[0:2] = [] # We can remove items together • a[:] = [] # Clear the list
  12. 12. Lists in detail • a.append(25) # adds an element at the end of list • b =[55,66,77] a.extend(b) a=a+b; • a.insert(1,99) # Inserts 99 at position 1 • a.pop(0) # pop elements at position 0 # Combines two lists
  13. 13. Strings char a[]=“baabtra”; a= ‘baabtra’ b=“doesn’t” C=“baabtra ”mentoring partner”” Strings are character lists, So can be used like any other lists as we discussed earlier print (a[0]) a.append(“m”); C Python
  14. 14. Strings in detail • String slicing word=‘hello baabtra’ print(word[6:] # prints baabtra word[: 6] # prints ‘hello ‘ word2= ‘good morning’ + word[6:] Print(word2) # prints ‘good morning baabtra‘
  15. 15. Control structures • Conditional Control Structures • If • If else • Switch • Loops • For • While • Do while Conditional Control Structures • If • If else • Switch Loops • For • While •Do while C Python
  16. 16. If else int a; Printf(“Enter the number”); scanf(“%d”,&a); If(a>80) Printf(“Distiction”); else if(a>60) Printf(“First class”); else { Printf(“Poor performancen”); Printf(“Repeat the examn”); } a=input(“Enter the number”) if a>80 : print(“Distinction”) elif a>60 : print(“First Class”) else : print(“Poor performance”) print(“Repeat the exam”) C Python
  17. 17. While Loop int i=0; whil(i<10) { printf(“%d”, i); i=i+1; } i=0 while i<10: print(i) i=i+1 C Python
  18. 18. For Loop int i=0; for(i=0;i<10;i++) { printf(“%d”, i); } It’s quite a bit untraditional . We need to define a range on which loop has to iterate. This can be done using Range(10,20) // creating a list with elements from 10 to 20 For i in range(10) : print(i) //print numbers up to 10 a=[12,14,16,’baabtra’] For i in a : print(i) //prints 12,14,16,baabtra C Python
  19. 19. Other Control structure statements • Break Eg: If(a%2==0) { Print(“even”); break; } • Break The break statement is allowed only inside a loop body. When break executes, the loop terminates. Eg: for x in range(2, n): if n % x == 0: print n, 'equals', x, '*', n/x break C Python
  20. 20. Other Control structure statements • Continue for(i=1;i<20;i++) { if(i%2==1) Continue; Print(“%d is even”,i); } • Continue The continue statement is allowed only inside a loop body. When continue executes, the current iteration of the loop body terminates, and execution continues with the next iteration of the loop Eg: For i in range(1,20) If i%2==0: continue print(“%d is even” %(i)) C Python
  21. 21. Other Control structure statements for(i=1;i<20;i++) { if(i%2==1) {} else Print(“%d is even”,i); } • pass The pass statement, which performs no action, can be used when you have nothing specific to do. Eg: if a<10: print(“less than 10”) elif x>20: pass # nothing to be done in this case Else: print(“in between 10 and 20”) C Python
  22. 22. Functions Int findSum(int a,int b) { int c; c=a+b; return c } d=findSum(10,15); def findSum(a,b) : return a+b sum=findSum(112,321) print(sum) C Python
  23. 23. Task • Write a simple python program which will have an array variable as below • a= [50,15,12,4,2] • Create 3 functions which will take the above array as argument and returns the arithmetic output –Add() //Outputs 83 –Substract() //Outputs 17 –Multiply() //Outputs 72000
  24. 24. That was the comparison ! So what’s new in python?
  25. 25. Sequences
  26. 26. Sequences • A sequence is an ordered container of items, indexed by non- negative integers. Python provides built-in sequence types ,they are:- – Strings (plain and Unicode), // We already have discussed – Tuples – Lists // We already have discussed
  27. 27. Tuples
  28. 28. Tuples • A tuple is an immutable ordered sequence of items which may be of different types. – (100,200,300) # Tuple with three items – (3.14,) # Tuple with one item – ( ) # Empty tuple • Immutable means we cant change the values of a tuple • A tuple with exactly two items is also often called a pair.
  29. 29. Operation on Tuples tpl_laptop = ('acer','lenova','hp','TOSHIBA') tpl_numbers = (10,250,10,21,10) tpl_numbers.count(10) # prints 3 tpl_laptop.index('hp') # prints 2
  30. 30. Task • Create a python program that will accept two tuples as arguments and return the difference between the tuple values,
  31. 31. Dictionaries
  32. 32. Dictionaries • A dictionary is an arbitrary collection of objects indexed by nearly arbitrary values called keys. They are mutable and, unlike sequences, are unordered. –Eg :{ 'x':42, 'y':3.14, 'z':7 } –dict([[1,2],[3,4]]) # similar to {1:2,3:4}
  33. 33. Operation on Dictionaries • dic={'a':1,'b':2,'c':3} – len(dic) # returns 3 – del dic['a'] # removes element with key ‘a’ – a in dic # returns ‘True’ .Bur – dic.items() #Displays elements – for i in dic.iterkeys(): ... print i # Returns key – for i in dic. itervalues(): ... print i # Return values
  34. 34. Task • Write a python program with a dictionary variable with key as English word and value as meaning of the word. • User should be able to give an input value which must be checked whether exist inside the dictionary or not and if it is there print the meaning of that word
  35. 35. Sets
  36. 36. Sets • Sets are unordered collections of unique (non duplicate) elements. – St= set(‘baabtra calicut’) – print (st) #prints {‘r’,’u’,’t’,’c’,’b’,’a’,’i’,’l’}
  37. 37. Operation on sets • st1=set(‘baabtracalicut’) • st2=set(‘baabtra’) – st1.issubset(st2) #Returns true – st2.issuperset(st1) #Returns true – st1. remove(‘mentoringpartner') – st1. remove(‘calicut)
  38. 38. Questions? “A good question deserve a good grade…”
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