Python File Handling

File Handling

File handling is an important part of any web application. 
Python provides inbuilt functions for creating, writing, and reading files.
There are two types of files that can be handled in python,normal text
files and binary files.

By using the below modes we can read or write into the files 

There are four different methods (modes) for opening a file: 

"r" - Read - Default value. Opens a file for reading, error if the file does

not exist 

"a" - Append - Opens a file for appending, creates the file if it does not

exist 

"w" - Write - Opens a file for writing, creates the file if it does not exist

"x" - Create - Creates the specified file, returns an error if the file exists 

"t" - Text - Default value. Text mode 

"b" - Binary - Binary mode (e.g. images) 

We can perform read and write simultaniously by using the below modes

Read and Write (‘r+’): Open the file for reading and writing. The

handle is positioned at the beginning of the file. Raises I/O error if the

file does not exist. 

Write and Read (‘w+’) : Open the file for reading and writing. For an

existing file, data is truncated and over-written. The handle is

positioned at the beginning of the file. 

Append and Read (‘a+’) : Open the file for reading and writing. The file

is created if it does not exist. The handle is positioned at the end of the

file. The  data being written will be inserted at the end, after the existing

data. 

xb -- create binary

wb -- write binary 

ab -- append binary 

rb -- read binary

file built in functions -- open()

file built in methods -- read()--reads entire file ,readline() -- here we need to give number to read those many charecters,readlines() -- it prints all lines in the form of list. -- all these are for to read

write() -- to write

close() -- to close

seek() -- To change file position 

tell() -- Returns the currentfile position

--Create file example

f = open("C:/Desktop/file.txt", "x")

f.close()  

--To open a file and write

--Write method will delete the old data and writes new data.

f = open("file.txt", "w") 

f.write("hellow")

f.close()

-- Append method

f.append("hellow")

f.close()

By looping through the lines of the file, you can read the whole file, line by line: 

f = open("C:/Desktop/file.txt", "r")

for x in f: 

    print (x)

f.close()