Python File handling is an important part of any web application. It is nothing but, the operating system uses the filehandle internally when accessing the file. It is a special area of main memory that is reserved for file handling, and the size of the area determines how many files can be open at once.
Python File Handling
Python has several functions for creating, reading, updating and deleting files.
Methods for Opening File in Python
There are 4 methods for opening files. open( ) function has two parameters i.e filename and mode.
| Modes | Function | Description |
|---|---|---|
| “r” | Read | Opens a file for reading, and shows an error if the file doesn’t exist |
| “a” | Append | Opens a file for appending, creates if a file doesn’t exist |
| “w” | Write | Opens a file for writing, creates if the file doesn’t exist |
| “x” | Create | Creates a specified file and returns an error if the files exist |
| “t” | text | It gives default values, in text mode |
| “b” | Binary | binary mode (ex: images) |
Syntax
To open a file for reading it is:
f = open(“demofile.txt”)
The above syntax is same as : f = open(“demofile.txt”, “rt”)
Here, “r” & “t” are default values, you do not need to specify them.
Reading & Writing Files in Python
The file object provides a set of access methods for accessing the files easier.
Read( ) method
It reads a string from an open file. Remember that Python strings have binary data, apart from text data.
Syntax: fileObject.read([count]);
Example
# Open a file
fo = open("foo.txt", "r+")
str = fo.read(10);
print "FreshersnowString is : ",str#
Close opened filefo.close()
Output: Read String is: Freshersnow is
Write( ) Method
It writes any string to open files. Remember that Python strings have binary data, but not only text.
Syntax: fileObject.write(string);
Example
# Open a filefo = open("foo.txt", "wb")
fo.write( "Freshersnow is awesome.\nHey Freshersnow!!\n");
#Close opend filefo.close()
Output
Freshersnow is awesome.
Hey Freshersnow
Read Lines( )
We can read the lines by using the readline( ) method.
Example
f = open("demofile.txt", "r")
print(f.readline())
Output: Hello! Welcome to demofile.txt
Renaming & Deleting files in Python
By using python file handling commands or methods we can also delete and rename the files.
rename( ) method
It will be taking two arguments. i.e current file name & new file name.
Syntax: os.rename(current_file_name, new_file_name)
Example
import osos.rename( "test1.txt", "test2.txt" )
remove( ) method
we can use the remove( ) method to delete files.
Syntax: os.remove(file_name)
Example
import
osos.remove("text2.txt")
Directories in Python
All the python file handling is stored at different directories. They are as follows:
mkdir( ) method
It helps you to create files in the new directory.
Syntax: ab.mkdir(“newdir”)
Example
import os
ab.mkdir("test")
chdir( ) method
You can use this method to change the directory.
Syntax: ab.chdir(“newdir”)
Example
import os
os.chdir("/home/newdir")
getcwd( ) method
It displays the current working directory.
Syntax: os.getcwd()
Example
import os os.getcwd()
rmdir( ) method
It deletes the directory which is passed through an argument in methods. Before removing the directory all the content should be removed.
Syntax: os.rmdir(‘dirname’)
Example
import osos.rmdir( "/tmp/test" )
Close files
After finishing the task try to close the files.
Example
f = open("demofile.txt", "r")
print(f.readline( ))
f.close( )
Output: Hello! Welcome to demofile.txt