16 file handling in python

 1. Using file handling we can do file operations

# How to open a file in python ?

1. We can open a file two ways in python 

    1. open()

    2. With open()

# OPEN

1. Using open we can open only one file at a time and we have to close a file explicity

# WITH OPEN 

1. Using with open we can open multiple files at a time and no need to close files explicity

# File Open Modes In Python

r    ==>     It opens a file for read only.

w    ==>     It allows write-level access to a file. If the file already exists, then it’ll get overwritten. It’ll create a new file if the same doesn’t exist.

a    ==>     It opens the file in append mode.

a+   ==>     It opens a file FOR append AND read

rb   ==>     It opens a binary file for read

1)  Read file

fh = open('names.txt', 'r')

## To open a file from another path

#fw = open(r'C:\Users\smellamput001\Desktop\BACKUP_EPRO\RRR.txt', 'r')

## Using read we can read entire file data and return in string format

fdata = fh.read()

print(fdata)

## To read the first five characters

#fdata = fh.read(5)

#print(fdata)

## Using readline we can read only one line and return in string format

#line  = fh.readline()

#print(' 1 ', line)

#line  = fh.readline()

#print(' 2 ', line)

## Using readlines we can read total lines in a file and  return in list format

lines  = fh.readlines()

print(' READ LINES ', lines)

# To close a file

fh.close()

2) Write into file

'''

1. To do write operation on file we have to open a file with 'w' mode

2. If you open a file with write mode if file is not exist it will crate a new file, 

if file is exist it will remove old data and write new data.

'''

fw = open('RRRR.txt', 'w')

# To write data into file

fw.write('\nHi Good Morning\n')

fw.write('How are you')

# To close a file

fw.close()

3) Append the file

'''

1. To do append operation on file we have to open a file with 'a' mode

2. If you open a file with append mode 

if file is not exist it will crate file, 

if file is exist it will add new data after old data.

'''

fw = open('append_names.txt', 'a')

# To write data into file

fw.write('\nHi umamahesh\n')

fw.write('How are you\n ')

# To close a file

fw.close()

4) open the file using withopen() function

# reading names.txt and writing into names_write.txt

with open('names.txt') as fr, open('names_write.txt', 'w') as fw:

    fw.write(fr.read())

5 ) tell( function

'''

1. Tell is used to find the file handler position

'''

fh = open('names.txt')

# To know File handler position before read any data

print(' Before read :', fh.tell())

# Using readline we can read only one line and return in string format

line  = fh.readline()

# To know File handler position after read a line

print(' After read :', fh.tell())

# To close a file

fh.close()

5) Seek()

'''

1. Seek is used to bring the file handler position 

where ever we required

'''

fh = open('names.txt', 'r')

## reading entire data from file

line  = fh.read()

## If you wnat to bring file handler position to starting

print(' FH position Before seek :', fh.tell())

fh.seek(8)

print(' FH position After seek  :', fh.tell())

print(' 1 : ',fh.readline())

## If you wnat to bring file handler to 8th position

#print(' FH position Before seek :', fh.tell())

#fh.seek(8)

#print(' FH position After seek  :', fh.tell())

#print(fh.readline())

# To close a file

fh.close()