filehandling in python

File handling is the important chapter to read in the programming language which helps to read, write files along with many other file handling options, to operate on files.

The concept of file handling has stretched over various other languages, but the implementation is either complicated or lengthy, but alike other concept of python this concept here is also easy and short.

  •  r “, for reading.
  •  w “, for writing.
  •  a “, for appending.
  •  r+ “, for both reading and writing
# a file named "filename", will be opened with the reading mode. 
file = open('filename.txt', 'r') 
# This will print every line one by one in the file 
for data in file: 
    print (data) 

Working with read() mode

we use file.read() to work on the read mode. read() is used to read the data from the file

# Python code to illustrate read() mode 
file = open("filename.text", "r")  
print file.read() 

Creating a file using write() mode

Basically write() function is used to write the data in a txt file.

# Python code to create a file 
file = open('filename.txt','w') 
file.write("This is the write command") 
file.write("It allows us to write in a particular file") 
file.close() 

Working with append() mode

append() is used to push the data in a file,

# Python code to illustrate append() mode 
file = open('filename.txt','a') 
file.write("This will add this line") 
file.close() 

Login system using the file handling


import os.path  

if not os.path.exists('register.txt'):  
    file = open('register.txt', 'w')
    file.close()  # close garnu parxa file lai


def register():  
    username = input('Enter username: ')
    if username in open('register.txt', 'r').read(): 
        print('Username pahile thiyo ')
        exit()  # if bata bahira aayeko
    password = input('Enter password: ')
    c_password = input('Enter confirm password: ')
    if password != c_password:
        print('Sorry kanchaa yespali')
        exit()
    handle = open('register.txt', 'a')  
    handle.write(username) 
    handle.write(' ')
    handle.write(password)  # password write garyo
    handle.write('\n')
    handle.close()
    print('Successfully register')
    exit()


def login():
    username = input('Enter username: ')
    password = input('Enter password: ')
    get_data = open('register.txt', 'r').readlines() 
    users_data = []     
    for user in get_data:      
        users_data.append(user.split())  
    total_user = len(users_data)    
    increment = 0
    login_success = 0
    while increment < total_user:
        usernames = users_data[increment][0]
        passwords = users_data[increment][1]
        if username == usernames and password == passwords:
            login_success = 1

        increment += 1

    if login_success == 1:
        print('Welcome ' + username)
    else:
        print('invalid username & password')
        register()


login()

File handling with csv

import csv
import os.path

with open('student.csv') as student_list:
    data = csv.reader(student_list)
    for user in data:
        y= user[1]
        z = user[2]
        x= user[0]
        if x[0] is "a":
            file = open('student.txt', 'a')
            file.write(x+" ")
            file.write(y+ " ")
            file.write(z+" ")
            file.write('\n')
            file.close()

        elif x[0] is "r":
                file = open('students.txt', 'a')
                file.write(x+ " ")
                file.write(y+ " ")
                file.write(z+ " ")
                file.write('\n')
                file.close()

student.csv contains the following data

name,age,phone
achyut,22,9843450482
ram,24,98435371
anusha,22,985694731
akash,21,98545273
aliza,21,98611232

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