Learning python -Day 9

DAY 9

Exceptional handling

If we write a code

a=int(input("Enter a number"))
b=int(input("Enter 2nd number"))
c=a/b
print(c)

run the function CTL+shift+fn+F10

as long as a  and b values are non zero, it will deliver a value

Enter a number4

Enter 2nd number2

2.0

However if the value changes to zero then we get the output

Enter a number4

Enter 2nd number0

Traceback (most recent call last):

  File "C:/Users/AbhishekSingh/PycharmProjects/First Project/venv/exc2.py", line 3, in <module>

    c=a/b

ZeroDivisionError: division by zero

To handle this exception we use Try and except commands

try:
    a=int(input("Enter a number"))
    b=int(input("Enter 2nd number"))
    c=a/b
    print(c)
except ZeroDivisionError:
    print("Value can't be zero")
except ValueError:
    print("Enter only integer value")
    print("Hello")

run the function CTL+shift+fn+F10

Enter a number4

Enter 2nd number0

Value can't be zero

Or

Enter a numberasasasa

Enter only integer value

Hello

We use finally command to make sure no what what exception occurs, final command gets executed

try:
    a=int(input("Enter a number"))
    b=int(input("Enter 2nd number"))
    c=a/b
    print(c)
except ZeroDivisionError:
    print("Value can't be zero")
finally:
    print("Hello")

run the function CTL+shift+fn+F10

Enter a number4

Enter 2nd number0

Value can't be zero

Hello

You cant remember all the exception errors. So to take care of that we use standalone exception

try:
    a=int(input("Enter a number"))
    b=int(input("Enter 2nd number"))
    c=a/b
    print(c)
except ZeroDivisionError:
    print("Value can't be zero")
except ValueError:
    print("Enter only integer value")
except:
    print("Enter valid number")
finally:
    print("Hello")

run the function CTL+shift+fn+F10

Enter a number6

Enter 2nd number0

Value can't be zero

Hello

You can use else command also if no exception occurs in your program

try:
    a=int(input("Enter a number"))
    b=int(input("Enter 2nd number"))
    c=a/b
    print(c)
except ZeroDivisionError:
    print("Value can't be zero")
except ValueError:
    print("Enter only integer value")
except:
    print("Enter valid number")
else:
    print("No Exception")
finally:
    print("Hello")

run the function CTL+shift+fn+F10

Enter a number4

Enter 2nd number2

2.0

No Exception

Hello

FILE HANDLING

f=open("abc.txt","w")

the in the above line, open is used to open a file if the file exists, if not then it will create a new file. It will write over existing file if existing file exists

“w” is the command for writing, “r” is for reading and “a” for appending

f=open("abc.txt","w")
f.write("This is first file program\n")
f.write("I'm enjoying\n")
f.write("This is python")
f.close()

run the function CTL+shift+fn+F10

abc.txt gets created with contents

This is first file program
I'm enjoying
This is python

f=open("abc.txt","r")
s=f.read()
print(s)
f.close()

run the function CTL+shift+fn+F10

This is first file program

I'm enjoying

This is python

f=open("abc.txt","r")
s=f.readlines()
print(s)
f.close()

run the function CTL+shift+fn+F10

['This is first file program\n', "I'm enjoying\n", 'This is python']

f=open("abc.txt","r")
s=f.readline()
print(s)
f.close()

run the function CTL+shift+fn+F10

This is first file program

f=open("abc.txt","a")
f.write("This is first file program\n")
f.write("I'm enjoying\n")
f.write("This is python")
f.close()

run the function CTL+shift+fn+F10

This is first file program
I'm enjoying
This is pythonThis is first file program
I'm enjoying
This is python

To have read and write in same command

=open("abc.txt","w")
f.write("This is first file program\n")
f.write("I'm enjoying\n")
f.write("This is python")
f.close()
f=open("abc.txt","r")
s=f.read()
print(s)
f.close()

run the function CTL+shift+fn+F10

This is first file program

I'm enjoying

This is python

Or use

W+

f=open("abc.txt","w+")
f.write("This is first file program\n")
f.write("I'm enjoying\n")
f.write("This is python")

f.seek(0)
s=f.read()
print(s)
f.close()

run the function CTL+shift+fn+F10

This is first file program

I'm enjoying

This is python

In the above example we are using f.seek(0). It will take back to zero index, if you change zero to 1 or 2 then it will print from 1 or 2 index

To read file from your desktop

path="C:\\Users\\AbhishekSingh\\Desktop\\f1.txt"
f=open(path,"r")

s=f.read()
print(s)

f.close()

run the function CTL+shift+fn+F10

this is the new shit

If you look at the path

path="C:\\Users\\AbhishekSingh\\Desktop\\f1.txt"

normally path uses single \ and not double\\  in python \ menas going to another line so we would need to make single \ to double \\ in the path of the file

Renaming a file

import os
os.rename("abc.txt","cde.txt")

os is operating system

import os

src="C:\\Users\\AbhishekSingh\\Desktop\\f1.txt"
dst="C:\\Users\\AbhishekSingh\\Desktop\\f2.txt"

os.rename(src,dst)

import os


os.remove("C:\\Users\\AbhishekSingh\\Desktop\\f2.txt")

Learning Python- Day 10