Python provides built-in methods to read from and write to files using file objects. The most commonly used methods are:

• read() – Reads file content.
• write() – Writes data to a file.

---

🔹 Writing to a File Using write()

• You must open the file in write ('w') or append ('a') mode.
• The method returns the number of characters written.
• Existing content is overwritten in 'w' mode.

# Open a file in write mode
file = open("example.txt", "w")

# Write data to the file
file.write("Hello, World!\n")
file.write("Python file handling is simple.\n")

# Close the file
file.close()

✅ Output in example.txt:

Hello, World!
Python file handling is simple.

🔹 Appending to a File ('a' Mode)

file = open("example.txt", "a")
file.write("Appending a new line.\n")
file.close()

✅ Adds new content without overwriting existing data.

---

🔹 Reading from a File Using read()

To read a file, open it in read mode ('r').

# Open the file in read mode
file = open("example.txt", "r")

# Read the entire file content
content = file.read()

print(content)

# Close the file
file.close()

✅ Output (prints file content):

Hello, World!
Python file handling is simple.
Appending a new line.

🔹 Reading Only a Certain Number of Characters

file = open("example.txt", "r")
print(file.read(10))  # Reads only the first 10 characters
file.close()

✅ Output:

Hello, Wor

---

🔹 Reading Line by Line

🔹 Using readline() – Reads a Single Line

file = open("example.txt", "r")
print(file.readline())  # Reads the first line
file.close()

✅ Output:

Hello, World!

🔹 Using readlines() – Reads All Lines into a List

file = open("example.txt", "r")
lines = file.readlines()  # Returns a list of lines
file.close()

print(lines)

✅ Output:

['Hello, World!\n', 'Python file handling is simple.\n', 'Appending a new line.\n']

---

🔹 Best Practice: Using with open()

with open() automatically closes the file after reading or writing.

with open("example.txt", "r") as file:
    content = file.read()
    print(content)  # File is automatically closed after this block

---

🔹 Writing and Reading ('w+' and 'r+' Modes)

• 'w+' – Overwrites the file, then allows reading.
• 'r+' – Reads first, then allows writing.

🔹 Using 'w+' Mode

with open("example.txt", "w+") as file:
    file.write("New content.\n")  # Overwrites existing content
    file.seek(0)  # Move cursor back to the beginning
    print(file.read())  # Read the file

✅ Output:

New content.

🔹 Using 'r+' Mode

with open("example.txt", "r+") as file:
    print(file.read())  # Read the existing content
    file.write("\nAdding more data!")  # Write new data

✅ Appends data at the end while keeping old content.

---

🔹 Summary Table

Mode	Description
'r'	Read (default). File must exist.
'w'	Write (creates/overwrites file).
'a'	Append (adds data at the end).
'r+'	Read + Write (does not delete content).
'w+'	Write + Read (overwrites file).
'a+'	Append + Read (adds data, keeps old content).

Would you like examples for working with CSV files or binary files? 🚀