Opening a file in Python programming language

One of the key advantages of Python is its ability to handle a wide range of operations related to reading, writing and manipulating files. Opening a file is an essential operation in any programming language as it forms the basis for reading, writing, and manipulating data. In this tutorial, we will explore how to open a file in Python, different modes of opening files, and crucial things to keep in mind while opening files in Python. Join us as we delve into the world of file handling in Python!

Python open function 

• Python has a built-in function open() to open a file. 
• This function returns a file object, also called a handle, as it is used to read or modify the file accordingly. 
• We can specify the mode while opening a file. 
• In mode, we specify whether we want to 
  • read 'r', 
  • write 'w' or 
  • append 'a' to the file. 
• If we don't specify the mode, it defaults to 'r'. 
• The syntax of the  open()  function is :  file_object = open(file_name, access_mode, buffering) 

parameters we can pass to the open() function

• file_name : Name of the file to be opened.
• access_mode : Access modes for opening a file. For example, `r`, `w`, `a`, `x` etc.
• buffering (Optional): 0 to turn off buffering. Any positive value to indicate the buffer size.

Access Modes for Opening a file

Different characters for mentioning the file opening modes

`+`: Read and Write mode. The `r+` mode is used to open a file for both reading and writing operations.
`U`: This mode allows universal newline support. This mode is only available in Python 2.

Steps for opening file in python

• Open a file in the desired mode using the  open()  method. The function returns a file object.
• Perform read or write operations on the file.
• Close the file using the  close()  method.

Different scenarios for opening a file in python

How to open a file in read mode

• We can open a file in read mode by passing the value ‘r’ for the mode argument of the open() function.
• The  read()  method can then be used to read the file.
• Code Sample : 

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


# "example.txt" is the name of the file we want to open 
# "r" indicates that we want to read the file. 
# The code will print the entire contents of the file. 

How to open a file in write mode

• We can open a file in write mode by passing the value ‘w’ for the mode argument of the open() function.
• The  write()  method can then be used to write to the file.
• If the file already exists, opening it in write mode will delete the old contents of the file.
• Code Sample : 

file = open("example.txt", "w")
file.write("Hello, World!")
file.close()


# "example.txt" is the name of the file we want to open 
# "w" indicates that we want to write to the file. 
# The code will create the file if it does not exist 
# will overwrite the content if it does exist. 

How to open a file in append mode

• We can open a file in append mode by passing the value ‘a’ for the mode argument of the open() function.
• The  write()  method can then be used to write to the file.
• If the file already exists, data will be written to the end of the file, without deleting the old contents.
• Code Sample : 

file = open("example.txt", "a")
file.write("\nHello, World Again!")
file.close()

# "example.txt" is the name of the file we want to open 
# "a" indicates that we want to append to the file. 
# The code will create the file if it does not exist 
# and will append the content if it does.

How to open a file with relative path

• The  os.path.join()  method is used to join one or more path components in Python.
• This method will create a path with the appropriate separator, based on the operating system.
• We can pass this file path as the first argument of the open() function to open the file.
• Code Sample : 

import os

file_path = os.path.join("directory", "example.txt")
file = open(file_path, "r")
print(file.read())
file.close()

How to open a file using with statement

• The  with   statement is a better way to open files.
• It automatically closes the file after the block of code is executed.
• Code Sample : 

with open("example.txt", "r") as file:
   print(file.read())
   
   
   

How to open a file for multiple operations

• The `r+` mode is used to open a file for both reading and writing operations.
• We can then use the  read()  and  write()  methods in combination to perform multiple operations on a file.
• Code Sample : 

with open("example.txt", "r+") as file:
   print(file.read())
   file.write("\nAdded a new line!")
   
   
   

How to open a binary file

• The `rb` mode is used to open binary files.
• The  read()  method can be used to read binary data.
• Code Sample : 

with open("binaryfile.png", "rb") as file:
   print(file.read())
   
   
   

How to Handle the FileNotFoundError

• The python interpreter raises a   FileNotFoundError  error if the file specified in the open() function does not exist.
• The  os.path.exists()  method is used to check whether a file path exists or not.
• We can also use try-except blocks to handle file-not-found errors.
• Code Sample : 

import os

file_path = os.path.join("directory", "example.txt")

if os.path.exists(file_path):
   file = open(file_path, "r")
   print(file.read())
   file.close()
else:
   print("File does not exist.")
   
   
   
   

How to close a file

• It is always a good practice to close the file after using it.
• The  close()  method is used to close a file.