File operation for copying content of one file to another

#  Copying content of 1.txt file to 2.txt after creation of file
#  Please provide the 1.txt file in the current folder as input and
#  check after runing the program in the same folder for 2.txt

I=open('1.txt',"r")
O=open('2.txt',"w")
for l in I.readlines():
    O.write(l)
I.close()
O.close()

Exceptional handling for Zero Division Error

# if value of x is given as zero the zero divison error generates and program terminates
x=int(raw_input('Enter the number of students failed:'))
y=100/x
print y


# If x is not defined itself the program not terminated instead it goes to except loop
try:
    x=int(raw_input('Enter the number of students failed:'))
    y=100/x
    print y
except ZeroDivisionError:
    x=1
    y=100/x
    print y

Exceptional handling for Name Error

# If x is not defined itself the program not terminated
try:
    y=50*x
except NameError:
    x=1
    y=50*x
    print y
   

Exceptional handling for Key Error

#Without Exceptional handling program terminates if key b not found
s={'d':2,'k':4}
if b in s.keys():
    s['b'].append[9]
else:
    s['b']= 8


#Exceptional handling for key error and program run without termination
s={'d':2,'k':4}
try:
    s['b'].append[9]
except KeyError:
    s['b']= 8

Reverse of a number using functions

def intreverse(Number):
  Reverse = 0          # Initialize the reverse value to overcome garbage value storage
  while(Number > 0):
    Reminder = Number %10
    Reverse = (Reverse *10) + Reminder
    Number = Number//10
  return (Reverse)