Python File Open
File handling is an important part of any web application.
Python has several functions for creating, reading, updating, and deleting files.
File Handling
The key function for working with files in Python is the
open() function.
The open() function takes two parameters;
filename, and mode.
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
In addition you can specify if the file should be handled as binary or text mode
"t" - Text - Default value. Text mode
"b" - Binary - Binary mode (e.g.
images)
Syntax
To open a file for reading it is enough to specify the name of the file:
f = open("demofile.txt")
Open a File on the Server
Assume we have the following file, located in the same folder as Python:
f = open("demofile.txt", "r")
print(f.read())
If the file is located in a different location, you will have to specify the file path, like this:
f = open("D:\\myfiles\welcome.txt", "r")
print(f.read())
Read Only Parts of the File
By default the read() method returns the whole text, but you can also specify how many characters you want to return:
f = open("demofile.txt", "r")
print(f.read(5))
Python File Write
Write to an Existing File
To write to an existing file, you must add a parameter to the
open() function:
"a" - Append - will append to the end of the file
"w" - Write - will overwrite any existing content
f = open("demofile2.txt", "a")
f.write("Now the file has more content!")
f.close()
#open and read the file after the appending:
f =
open("demofile2.txt", "r")
print(f.read())
Open the file "demofile3.txt" and overwrite the content:
f = open("demofile3.txt", "w")
f.write("Woops! I have deleted the content!")
f.close()
#open and read the file after the appending:
f = open("demofile3.txt", "r")
print(f.read())
Create a New File
To create a new file in Python, use the open() method,
with one of the following parameters:
"x" - Create - will create a file, returns
an error if the file exist
"a" - Append - will create a file if the
specified file does not exist
"w" - Write - will create a file if the
specified file does not exist
Python Delete File
Delete a File
To delete a file, you must import the OS module, and run its
os.remove() function:
import os
os.remove("demofile.txt")
Check if File exist:
To avoid getting an error, you might want to check if the file exists before you try to delete it:
import os
if os.path.exists("demofile.txt"):
os.remove("demofile.txt")
else:
print("The file does not exist")
Delete Folder
To delete an entire folder, use the os.rmdir() method:
import os
os.rmdir("myfolder")
