Basic String Manipulations

word = 'banana talks'

for i in word:  #Here the i is the letters in the string word
      print 'Character from string:',i

for h in range(len(word)):   #Here the h is index created by range function with value created by length
      print 'Index:',h,'charater:' ,word[h]

n1 = word.upper()

print 'String in the upper case:', n1

n2 = word.lower()

print 'String in the lower case:', n2

print 'Display a part of string :',word[1:5] # It display string from index 1 to 4

print 'Display a part of string :',word[4:8] # It display string from index 4 to 7

Factorial of a Number

# Python program to find the factorial of a number provided by the user.


num = int(input("Enter a number: "))

factorial = 1

# check if the number is negative, positive or zero
if num < 0:
   print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
   print("The factorial of 0 is 1")
else:
   for i in range(1,num + 1):
       factorial = factorial*i
   print("The factorial of",num,"is",factorial)

Lisiting particular type of files in a directory

import os
Path = os.getcwd()
Names= os.listdir(Path)
h=raw_input('Enter the file type extension: ')
for n in Names:
      if h in n:
            print n

Enter the sum of n numbers using file

n=int(raw_input('Enter the n for sum of n numbers: '))
f=open('integers.txt','w')
for count in range(n+1):
      f.write(str(count)+"\n")
f.close()

f=open('integers.txt','r')
sum=0
for l in f:
      l=l.strip()
      number=int(l)
      sum+=number
print 'The sum is',sum

Writing and reading integers from a file

f=open('myfile.txt','w')
for count in  range(5):
      f.write(str(count))
f.close()
f=open('myfile.txt','r')
t=f.read()
print t

Writing and reading string from a file

f=open('myfile.txt','w')
f.write('\n Image Processing Research Group \n www.iprg.co.in \n')
f.close()
f=open('myfile.txt','r')
text=f.read()
print text

Basic operations in Python List

l=[]
n=int(raw_input('Enter the no of elements added to list:'))
for i in range(n):
      element=int(raw_input('Enter the elements:'))
      l.append(element)
print '\nNew List is ',
m=int(raw_input('\nEnter the no of elements added to list using insert:'))
for i in range(m):
      u=int(raw_input('Enter the index to be added'))
      u1=int(raw_input('Enter the element to be added'))
      l.insert(u,u1)
print '\nNew List after insert operation is:   ',l
ch=int(raw_input('\nPress 1 to pop the last element\nPress 2 to pop the element in a particular index\nEnter the choice: '))
if ch==1:
 l.pop()
 print '\nNew List after deletion is: ',l
elif ch==2:
 p=int(raw_input('Enter the element index to be deleted'))
 l.pop(p)
 print '\nNew List after deletion is: ',l
else:
  print '\nInvalid choice'
print ' \nList elements are sorted:  ',l

To add elements in list using insert

y=[]
n=int(raw_input('Enter the no of elements added to list:'))
index=0
for i in range(n):
      element=int(raw_input('Enter the elements:'))
      y.insert(index, element)
      index=index+1
print y

To add elements inside a list using append

l=[]
n=int(raw_input('Enter the no of elements added to list:'))
for i in range(n):
      element=int(raw_input('Enter the elements:'))
      l.append(element)
print l

To count the elements in a nested list with all elements are list

a=[[3, 4, 5,8, 8 ], [5, 6, 7], [7, 8, 9]]

def count(a):
 j=0
 n=0
 for b in a:
     j=len(b)
     n=n+j
 return n

t= count(a)
print "No elements in the nested list are:",t