File handling is an essential part of programming that allows you to read, write, update, and delete files from within your Python programs.
Python works with two major types of files: 1. Text Files and 2. Binary Files
| Feature | Text File | Binary File |
|---|---|---|
| Format | Human-readable | Machine-readable (0s and 1s) |
| Data Type | Textual data | Multimedia, image, audio, video etc. |
| File Modes | "r", "w", "a", etc. | "rb", "wb", "ab", etc. |
| Encoding | Usually uses UTF-8 | No encoding used |
| Examples | .txt, .csv, .py | .jpg, .mp3, .exe |
| Readable | Yes, by humans | No, only by programs |
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:
| Mode | Name | Description |
|---|---|---|
| "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
| Mode | Name | Description |
|---|---|---|
| "t" | Text | Default value. Text mode |
| "b" | Binary | Binary mode (e.g. images) |
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:
Syntax: file_object = open("filename.txt", "mode")
# Open and read a file
file = open("example.txt", "r") # Open in read mode
content = file.read() # Read full content
print(content)
After performing read/write operations, it’s important to close the file to free up system resources.
Note: You should always close your files. In some cases, due to buffering, changes made to a file may not show until you close the file.
# Using close()
file = open("example.txt", "r")
content = file.read()
print(content)
file.close() # Always close the file
# Recommended: Using with (Context Manager)
with open("example.txt", "r") as file:
content = file.read()
print(content)
# File is automatically closed after this block
In Python, you can create or modify a file using the write() methods. The file must be opened in a write mode:
"a" - Append - will append to the end of the file
"w" - Write - will overwrite any existing content
content = "Hello Students!\nWelcome to Python File Handling."
file = open("sample.txt", "w")
file.write(content)
file.close()
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| Function | Description | Example |
|---|---|---|
| open() | Opens a file and returns a file object | file = open("file.txt", "r") |
| read(size) | Reads specified number of characters | file.read(10) |
| readline() | Reads one line from the file | file.readline() |
| readlines() | Reads all lines and returns a list | file.readlines() |
| write() | Writes a string to the file | file.write("Hello") |
| writelines() | Writes list of strings to the file | file.writelines(["Hi", "Hello"]) |
| close() | Closes the file | file.close() |
| seek() | Moves the pointer to a specific byte | file.seek(0) |
| tell() | Returns current file pointer position | file.tell() |
| Property | Description | Example |
| name | Returns file name | file.name |
| mode | Returns access mode | file.mode |
| closed | Returns True if file is closed | file.closed |
The open() function is used to open a file and returns a file object. It is the starting point for any file operations in Python.
Syntax: file_object = open("filename", "mode")
file = open("example.txt", "r")
The read() function reads the content of the file. You can read the entire file or a specific number of characters.
Syntax: file.read(size)
# Read Entire File
file = open("example.txt", "r")
content = file.read()
print(content)
file.close()
# Read Specific Number of Characters
file = open("example.txt", "r")
content = file.read(6)
print(content)
file.close()
The readline() function reads one line from the file at a time. Each call to readline() reads the next line.
Syntax: file.readline()
file = open("example.txt", "r")
line1 = file.readline()
line2 = file.readline()
print("Line 1:", line1)
print("Line 2:", line2)
file.close()
The readlines() function reads all lines of a file and returns them as a list of strings. Each line becomes one element of the list.
Syntax: file.readlines()
file = open("example.txt", "r")
lines = file.readlines()
print(lines)
file.close()
The write() function is used to write a string to a file. If the file is opened in write ("w") or append ("a") mode, it will insert the content into the file.
Syntax: file.write(string)
file = open("example.txt", "w")
file.write("Python is fun!\n")
file.write("Let's learn file handling.")
file.close()
The writelines() function writes a list of strings to the file. Unlike write(), it can add multiple lines at once.
Syntax: file.writelines(list_of_strings)
lines = ["Hello Students!\n", "Welcome to Python File Handling.\n", "Enjoy Learning!\n"]
file = open("example.txt", "w")
file.writelines(lines)
file.close()
The seek() function is used to move the file cursor (pointer) to a specific position in the file. It helps you control where to read or write from.
Syntax: file.seek(offset, from_what)
offset: Number of bytes to move the cursor.
from_what: optional Reference position. Default is 0.
0 – Beginning of the file (default)
1 – Current file position
2 – End of the file
file = open("example.txt", "r")
file.seek(7) # Move to the 8th character (index 7)
content = file.read()
print(content)
file.close()
The tell() function returns the current position of the file cursor (in bytes) from the beginning of the file.
Syntax: file.tell()
file = open("example.txt", "r")
print("Initial position:", file.tell())
file.read(5)
print("Position after reading 5 characters:", file.tell())
file.close()
The close() function is used to close an open file. It is important to free up system resources and ensure that all data is properly written to disk.
Syntax: file.close()
file = open("example.txt", "w")
file.write("Closing the file after writing.")
file.close()
To work with binary files, use a b in the mode and using pickle Module to read and write Binary File.
✅ Write Data to a Binary File
Syntax: pickle.dump(object , file_handler) - used to write any object to the binary file.
import pickle
fruits = ["Apple", "Banana", "Mango", "Orange"]
file = open("fruits.dat", "wb") # open in binary write mode
pickle.dump(fruits, file) # serialize and save
file.close()
✅ Read Data from the Binary File
Syntax: Object = pickle.load(file_handler) - used to read object from the binary file.
import pickle
file = open("fruits.dat", "rb") # open in binary read mode
fruits = pickle.load(file) # deserialize
file.close()
print("Fruits List:", fruits)
Command Line Arguments allow you to pass values to your Python script when it is executed from the terminal or command prompt.
| Feature | Description | Example |
|---|---|---|
| Module | sys is used to fetch command-line arguments | import sys |
| Argument List | sys.argv returns arguments as a list of strings | sys.argv[1] gives 1st argument |
| Script Name | sys.argv[0] is always the script name | script.py |
| Number of Arguments | Use len(sys.argv) to count arguments | len(sys.argv) |
| Type Conversion | Arguments are strings, convert if needed | int(sys.argv[1]) |
import sys
# total arguments
n = len(sys.argv)
print("Total arguments passed:", n)
# Arguments passed
print("\nName of Python script:", sys.argv[0])
print("\nArguments passed:", end = " ")
for i in range(1, n):
print(sys.argv[i], end = " ")
# Addition of numbers
Sum = 0
# Using argparse module
for i in range(1, n):
Sum += int(sys.argv[i])
print("\n\nResult:", Sum)