Opening Files with Different Modes

Python's built-in open() function provides various modes to handle files. Below are common examples:

• Append mode (creates file if missing):

file_handle = open('data.txt', 'a')

• Binary mode (for images, etc.):

file_handle = open('photo.jpg', 'rb')

Reading File Content

Once a file is opened, you can read its contants using several methods.

2.1 Read Entire Content

Use .read() to load the whole file into a string.

with open('data.txt', 'r') as f:
    entire = f.read()
    print(entire)

2.2 Line-by-Line Reading

Use .readline() to fetch one line at a time.

with open('data.txt', 'r') as f:
    current = f.readline()
    while current:
        print(current, end='')
        current = f.readline()

2.3 Read All Lines into List

.readlines() returns a list of all lines.

with open('data.txt', 'r') as f:
    lines = f.readlines()
    for line in lines:
        print(line, end='')

Writing to Files

Writing behaviour depends on the mode used when opening the file.

3.1 Writing a Single Line

.write() writes a string to the file.

with open('data.txt', 'w') as f:
    f.write('First line\n')

3.2 Writing Multiple Lines

.writelines() accepts an iterable of strings.

records = ['Alpha\n', 'Beta\n', 'Gamma\n']
with open('data.txt', 'w') as f:
    f.writelines(records)

Iterating Over a File

File object are iterable, so you can use a for loop to read lines.

with open('data.txt', 'r') as f:
    for line in f:
        print(line, end='')

Context Manager (with Statement)

The with statement ensures proper resource cleanup. The file is automatically closed when the block exits.

with open('data.txt', 'r') as f:
    content = f.read()
    print(content)  # File closed after block

Exception Hnadling for Robustness

File operations can raise errors such as FileNotFoundError or PermissionError. Use try-except to handle them gracefully.

try:
    with open('missing.txt', 'r') as f:
        data = f.read()
        print(data)
except FileNotFoundError:
    print("File does not exist.")
except PermissionError:
    print("Permission denied.")
except Exception as e:
    print(f"An unexpected error occurred: {e}")

Manual File Closing

Although with is preferred, you can manually close a file using .close().

f = open('data.txt', 'r')
content = f.read()
print(content)
f.close()

Binary File Operations

For non-text files (e.g., images, audio), open in binary mode by adding 'b' to the mode string.

with open('photo.jpg', 'rb') as f:
    raw_data = f.read()
    # Process binary data

File Pointer Positioning

The .seek() method moves the file pointer to a specific byte position.

with open('data.txt', 'r') as f:
    first_chars = f.read(10)  # Read first 10 characters
    print(first_chars)
    f.seek(0)                 # Jump back to start
    again = f.read(5)
    print(again)