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Reading Files in Python

  • This lesson explains how to open and read data from files in Python.

  • What is File Handling?

    File handling allows a program to read data from files and write data into files.

    👉 Files are used to store data permanently.

    Examples:

    • Text files (.txt)

    • Data files

    • Log files

    • Images (binary files)

    Why Do We Need File Handling?

    File handling helps to:

    • Store data permanently

    • Read large data efficiently

    • Share data between programs

    • Handle real-world applications

    File Modes in Python

    When opening a file, we must specify a mode.

    Text Mode (t) – Default Mode

    • Used for text files

    • Reads data as string

    • Default mode in Python

    Mode

    Meaning

    r or rt

    Read text file

    Binary Mode (b)

    • Used for non-text files

    • Reads data as bytes

    • Used for images, audio, video

    Mode

    Meaning

    rb

    Read binary file

    Opening Files in Python

    open() Function

    file = open("filename", "mode")


    Part

    Description

    filename

    Name of the file

    mode

    File access mode

    open()

    Opens the file

    file

    File object

Opening a Text File

This program opens a file in read text mode. 

file = open("data.txt", "r")
print("File opened successfully")
file.close()

  • Reading Entire File

    Using read()

    The read() method reads the entire content of the file.

Reading Entire File Using read()

This program reads and prints the complete content of the file. 

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

  • Reading Line by Line

    Method 1: readline()

    Reads one line at a time.


Reading One Line Using readline()

This program reads only the first line of the file. 

file = open("data.txt", "r")
line = file.readline()
print(line)
file.close()

  • Method 2: readlines()

    Reads all lines and stores them in a list.

Reading Lines Using readlines()

This program reads all lines and prints them as a list. 

file = open("data.txt", "r")
lines = file.readlines()
print(lines)
file.close()
  • Method 3: Reading File Using Loop

Reading File Using for Loop

This program reads and prints each line one by one. 

file = open("data.txt", "r")

for line in file:
    print(line)

file.close()

  • Reading Binary Files

    When to Use Binary Mode?

    Binary mode is used for:

    • Images

    • PDFs

    • Audio / video files

Reading Binary File

This program opens a binary file and reads its content. 

file = open("image.jpg", "rb")
data = file.read()
print(data)
file.close()

  • Using with Statement 

    Why Use with?

    • Automatically closes file

    • Safer and cleaner code

Using with Statement

This program reads file content without manually closing it. 

with open("data.txt", "r") as file:
    content = file.read()
    print(content)
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