PYTHON FILE HANDLING, CREATE-WRITE-READ-REMOVE FILES

F
ILE HANDLING, CREATE-WRITE-READ-REMOVE 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)

Open a File
To open the file, use the built-in open() function.
The open() function returns a file object, which has a read() method for reading the content of the file:
demofile.txt

Hello! Welcome to demofile.txt
This file is for testing purposes.
Good Luck!

f = open("demofile.txt", "r")
print(f.read())

Hello! Welcome to demofile.txt
This file is for testing purposes.
Good Luck!

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))

Hello

Read Lines
You can return one line by using the readline() method:

f = open("demofile.txt", "r")
print(f.readline())

Hello! Welcome to demofile.txt

By calling readline() two times, you can read the two first lines:

f = open("demofile.txt", "r")
print(f.readline())
print(f.readline())

Hello! Welcome to demofile.txt
This file is for testing purposes.

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

f = open("demofile.txt", "r")
for x in f:
print(x)

Hello! Welcome to demofile.txt
This file is for testing purposes.
Good Luck!

Close Files
It is a good practice to always close the file when you are done with it.

f = open("demofile.txt", "r")
print(f.readline())
f.close()

Hello! Welcome to demofile.txt

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
Note: the "w" method will overwrite the entire file.

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

Create a file called "myfile.txt":
f = open("myfile.txt", "x")

Create a new file if it does not exist:
f = open("myfile.txt", "w")

Delete a File
To delete a file, you must import the OS module, and run its os.remove() function:

Remove the file "demofile.txt":
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:
Check if file exists, then 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:
Remove the folder "myfolder":
import os
os.rmdir("myfolder")

Note: You can only remove empty folders.