Cleo_patra - Droid

1. Introduction

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File handling is one of the most important skills in Python. Almost every real-world application needs to read from or write to a file. Python makes file handling simple with built-in functions and context managers.

2. Opening and Closing Files

To work with a file, you first need to open it using the built-in open() function.

# Open a file for reading
file = open("example.txt", "r")
content = file.read()
print(content)
file.close()  # Always close the file

File Modes in Python:

Mode	Description
`"r"`	Read (default) – file must exist
`"w"`	Write – creates new file or overwrites existing
`"a"`	Append – adds new content without deleting old data
`"x"`	Create – fails if file already exists
`"b"`	Binary mode (e.g., images, videos)
`"t"`	Text mode (default)

3. Reading Files

Python offers multiple ways to read a file:

# Read entire file
with open("example.txt", "r") as f:
    data = f.read()
    print(data)

# Read line by line
with open("example.txt", "r") as f:
    for line in f:
        print(line.strip())

# Read specific number of characters
with open("example.txt", "r") as f:
    partial = f.read(10)  # first 10 characters
    print(partial)

4. Writing to Files

# Write (overwrites file if it exists)
with open("example.txt", "w") as f:
    f.write("Hello, Python!\n")
    f.write("File handling is easy.")

# Append new data
with open("example.txt", "a") as f:
    f.write("\nThis line is added at the end.")

5. Working with Binary Files

# Copy an image file
with open("image.jpg", "rb") as src:
    with open("copy.jpg", "wb") as dest:
        dest.write(src.read())

6. Best Practices

✅ Use with open() to ensure files are automatically closed.
✅ Handle errors using try...except.
✅ Always specify the correct encoding (encoding="utf-8") for text files.

7. Example: Word Counter Program

def count_words(filename):
    try:
        with open(filename, "r", encoding="utf-8") as f:
            text = f.read()
            words = text.split()
            return len(words)
    except FileNotFoundError:
        return "File not found."

print(count_words("example.txt"))