introduction to python
TRANSCRIPT
Introduction To PythonBasics, sequences, Dictionaries, Sets
Python
– Python is an interepted language, which can save you considerable time during program development because no compilation and linking is necessary.
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
C Vs PythonSyntax comparison
Commenting
// comment single line
/* comment multiple lines */
# comment single line
“ ” ” comment multiple lines “ ” ”
C Python
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 = 10a, b, c = 1, 2, "john"
C Python
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=10b=25print(a,b)
print (“value of a=%d and b= %d” % (a,b))
C Python
InPut
int a;Printf(“Enter the
number”);scanf(“%d”,&a);
a=input(“Enter the number”)
C Python
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
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
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
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
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
Strings in detail
• String slicingword=‘hello baabtra’print(word[6:] # prints baabtraword[: 6] # prints ‘hello ‘
word2= ‘good morning’ + word[6:]Print(word2) # prints ‘good
morning baabtra‘
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
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 performance\n”);Printf(“Repeat the exam\n”); }
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
While Loop
int i=0;whil(i<10){
printf(“%d”, i);i=i+1;
}
i=0while i<10: print(i) i=i+1
C Python
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 usingRange(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
Other Control structure statements
• Break
Eg: If(a%2==0) { Print(“even”); break; }
• BreakThe 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
Other Control structure statements
• Continue
for(i=1;i<20;i++){
if(i%2==1) Continue;Print(“%d is even”,i);}
• ContinueThe 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 loopEg:For i in range(1,20) If i%2==0: continue print(“%d is even” %(i))
C Python
Other Control structure statements
for(i=1;i<20;i++){
if(i%2==1) {}
else Print(“%d is even”,i);
}
• passThe 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
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
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
That was the comparison !
So what’s new in python?
Sequences
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
Tuples
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.
Operation on Tuples
tpl_laptop = ('acer','lenova','hp','TOSHIBA') tpl_numbers = (10,250,10,21,10)
tpl_numbers.count(10) # prints 3tpl_laptop.index('hp') # prints 2
Task
• Create a python program that will accept two tuples as arguments and return the difference between the tuple values,
Dictionaries
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}
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
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
Sets
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’}
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)
Questions?“A good question deserve a
good grade…”