The open() function in Python is used to create file objects, which allow us to read, write, or manipulate files.

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🔹 Syntax of open()

file_object = open("filename", mode)

• "filename": Name of the file (with extension, e.g., "data.txt").
• mode: Specifies how the file should be opened (read, write, append, etc.).

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🔹 File Open Modes

Mode	Description
'r'	Read (default mode). Fails if the file does not exist.
'w'	Write. Creates a new file or overwrites an existing file.
'a'	Append. Adds new content at the end of the file.
'x'	Create. Fails if the file already exists.
'b'	Binary mode. Used for images, videos, etc. (e.g., 'rb', 'wb').
't'	Text mode (default). Used for text files.
'+'	Read and write mode (e.g., 'r+', 'w+', 'a+').

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🔹 Creating a File Object

1️⃣ Opening a File for Writing ('w')

file = open("example.txt", "w")  # Opens a file in write mode
file.write("Hello, Python!\n")   # Writes data to the file
file.close()                     # Closes the file

✅ If "example.txt" does not exist, it creates it.
⚠️ If it exists, it overwrites the content.

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2️⃣ Opening a File for Reading ('r')

file = open("example.txt", "r")  # Opens file in read mode
content = file.read()            # Reads the file
print(content)                   # Prints the content
file.close()                      # Closes the file

✅ If the file does not exist, it raises a FileNotFoundError.

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3️⃣ Opening a File for Appending ('a')

file = open("example.txt", "a")  # Opens file in append mode
file.write("Adding more text!\n")  # Appends text to the file
file.close()

✅ New content is added at the end of the file without deleting existing data.

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4️⃣ Opening a File in Binary Mode ('rb', 'wb')

Used for images, videos, or binary files.

file = open("image.jpg", "rb")  # Opens an image file in binary read mode
data = file.read()
file.close()

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5️⃣ Using with open() (Recommended)

Using with open(), the file automatically closes after execution.

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

✅ Best Practice: Prevents errors due to forgetting file.close().

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🔹 Checking if a File Exists Before Opening

import os

if os.path.exists("example.txt"):
    with open("example.txt", "r") as file:
        print(file.read())
else:
    print("File not found!")

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🔹 Opening a File for Both Reading and Writing ('r+', 'w+', 'a+')

Read & Write ('r+')

with open("example.txt", "r+") as file:
    content = file.read()
    file.write("\nNew line added!")

✅ Reads existing content before writing.

Write & Read ('w+')

with open("example.txt", "w+") as file:
    file.write("Overwriting everything!\n")
    file.seek(0)  # Moves cursor to the beginning
    print(file.read())  # Reads the updated content

⚠️ Overwrites the entire file.

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🔹 Summary

Mode	Usage
'r'	Read file (error if file doesn’t exist).
'w'	Write file (creates/overwrites file).
'a'	Append file (adds new content).
'x'	Create file (error if file exists).
'b'	Binary mode ('rb', 'wb' for images, videos).
'+'	Read + Write ('r+', 'w+', 'a+').

Would you like a real-world example, like a log file system? 🚀