File Handling in Python - GeeksforGeeks

24 Dec, 2021
Python too 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 file differently as text or binary and this is important. Each line of code includes a sequence of characters and they form 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 Reading and Writing files.  
Before performing any operation on the file like read or write, 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:
r: open an existing file for a read operation.w: open an existing file for a write operation. If the file already contains some data then it will be overridden.a:  open an existing file for append operation. It won’t override existing data. r+:  To read and write data into the file. The previous data in the file will not be deleted.w+: To write and read data. It will override existing data.a+: To append and read data from the file. It won’t override existing data.
r: open an existing file for a read operation.
w: open an existing file for a write operation. If the file already contains some data then it will be overridden.
a:  open an existing file for append operation. It won’t override existing data.
 r+:  To read and write data into the file. The previous data in the file will not be deleted.
w+: To write and read data. It will override existing data.
a+: To append and read data from the file. It won’t override existing data.
Take a look at the below example:
Python3
# a file named "geek", will be opened with the reading mode.file = open('geek.txt', 'r')# This will print every line one by one in the filefor each in file:    print (each)
The open command will open the file in the read mode and the for loop will print each line present in the file.  
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: 
Python3
# Python code to illustrate read() modefile = 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: 
Python3
# Python code to illustrate read() mode character wisefile = open("file.txt", "r")print (file.read(5))
Let’s see how to create a file and how write mode works: To manipulate the file, write the following in your Python environment: 
Python3
# Python code to create a filefile = open('geek.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.  
Let’s see how the append mode works: 
Python3
# Python code to illustrate append() modefile = 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: 
rstrip(): This function strips each line of a file off spaces from the right-hand side.
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. Example: 
Python3
# Python code to illustrate with()with open("file.txt") as file:     data = file.read()# do something with data
We can also use the write function along with the  with() function: 
Python3
# Python code to illustrate with() alongwith write()with open("file.txt", "w") as f:    f.write("Hello World!!!")
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:
Python3
# Python code to illustrate split() functionwith open("file.text", "r") as file:    data = file.readlines()    for line in data:        word = line.split()        print (word)
There are also various other functions that help to manipulate the files and their contents. One can explore various other functions in Python Docs. 
This article is contributed by Chinmoy Lenka. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above 
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