File Handling in Python

Python supports file handling and allows users to handle files i.e., to read and write files, along with many other file handling options, to operate on files.
The concept of file handling has stretched over various other languages, but the implementation is either complicated or lengthy, but like other concepts of Python, this concept here is also easy and short.
Python treats files differently as text or binary and this is important. Each line of code includes a sequence of characters and they form a text file.
Each line of a file is terminated with a special character, called the EOL or End of Line characters like comma {,} or newline character.
It ends the current line and tells the interpreter a new one has begun. Let’s start with the reading and writing files.
File handling is an important part of any web application.
Python has several functions for creating, reading, updating, and deleting files.

Open() Function

Before performing any operation on the file like reading or writing, first, we have to open that file.
For this, we should use Python’s inbuilt function open() but at the time of opening, we have to specify the mode, which represents the purpose of the opening file.

f = open(filename, mode)

Where the following mode is supported:

1. r: open an existing file for a read operation.
2. w: open an existing file for a write operation. If the file already contains some data then it will be overridden.
3. a: open an existing file for append operation. It won’t override existing data.
4. r+: To read and write data into the file. The previous data in the file will be overridden.
5. w+: To write and read data. It will override existing data.
6. a+: To append and read data from the file. It won’t override existing data.

Take a look at the below example:

file = open('abcd.txt', 'r')
for i in file:
    print(i)

The open command will open the file in the read mode and the for loop will print each line present in the file.

Read() Mode

There is more than one way to read a file in Python.
If you need to extract a string that contains all characters in the file then we can use file.read().
The full code would work like this:

file = open("file.txt", "r")
print(file.read())

Another way to read a file is to call a certain number of characters like in the following code the interpreter will read the first five characters of stored data and return it as a string:

file = open("file.txt", "r")
print(file.read(5))

Creating a file using write() mode

Let’s see how to create a file and how to write mode works, so in order to manipulate the file, write the following in your Python environment.

file = open('abcd.txt','w')
file.write("This is the write command")
file.write("It allows us to write in a particular file")
file.close()

The close() command terminates all the resources in use and frees the system of this particular program.

Working of append() mode

Let us see how the append mode works:

file = open('geek.txt','a')
file.write("This will add this line")
file.close()

There are also various other commands in file handling that is used to handle various tasks like:

1. rstrip(): This function strips each line of a file off spaces from the right-hand side.
2. lstrip(): This function strips each line of a file off spaces from the left-hand side.

It is designed to provide much cleaner syntax and exception handling when you are working with code.
That explains why it’s good practice to use them with a statement where applicable.
This is helpful because using this method any files opened will be closed automatically after one is done, so auto-cleanup.

Using write along with the with() function

We can also use the write function along with the with() function:

with open("file.txt", "w") as f:
    f.write("Hello World!!!")

Split() using file handling

We can also split lines using file handling in Python. This splits the variable when space is encountered.
You can also split using any characters as we wish. Here is the code.

with open("file.text", "r") as file:
    data = file.readlines()
    for i in data:
        i = line.split()
        print(i)

There are also various other functions that help to manipulate the files and their contents. One can explore various other functions in Python Docs.