Python provides built-in functions to handle files. The most common operations are:

1. Opening a File

Use the built-in open() function:

file = open('filename.txt', mode)

• 'filename.txt' is the file name (and path if not in the current directory).

• mode is the mode in which you open the file. Common modes:

  • 'r' — read (default)

  • 'w' — write (creates or truncates file)

  • 'a' — append (write data to the end)

  • 'b' — binary mode (used with other modes, like 'rb' or 'wb')

  • 'x' — create a new file and open it for writing (error if exists)

  • '+' — read and write (e.g., 'r+', 'w+')

2. Reading from a File

• Read whole file:

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

• Read line by line:

file = open('example.txt', 'r')
for line in file:
    print(line.strip())  # strip removes trailing newline
file.close()

• Read a single line:

file = open('example.txt', 'r')
line = file.readline()
print(line)
file.close()

• Read lines as list:

file = open('example.txt', 'r')
lines = file.readlines()
print(lines)
file.close()

3. Writing to a File

• Overwrite or create file and write:

file = open('example.txt', 'w')
file.write("Hello, world!\n")
file.write("Welcome to file operations in Python.\n")
file.close()

• Append to a file:

file = open('example.txt', 'a')
file.write("This will be added at the end.\n")
file.close()

4. Closing a File

After file operations, always close the file to free resources:

file.close()

5. Using with Statement (Recommended)

Using with automatically closes the file when the block is exited, even if an error occurs.

with open('example.txt', 'r') as file:
    content = file.read()
    print(content)
# No need to call file.close()

6. Other Useful File Operations

• Check if file exists:

import os
if os.path.exists('example.txt'):
    print("File exists")
else:
    print("File does not exist")

• Rename or delete file:

import os
os.rename('old.txt', 'new.txt')
os.remove('example.txt')

Summary Table of Modes