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FILE IO in python with Example

 # File I/O

file = open("filename", "r")   # Open file for reading
content = file.read()          # Read file content
file.close()                   # Close the file

file = open("filename", "w")   # Open file for writing
file.write("Content")          # Write content to the file
file.close()                   # Close the file
 
File I/O in Python allows you to read from and write to files. Python provides various built-in functions and methods to handle file operations. Let's go through some examples to illustrate how to use File I/O in Python.

1. Reading from a File:
Suppose you have a file named "example.txt" with the following content:

```
Hello, this is an example file.
I am demonstrating file I/O in Python.
```

Now, let's read the contents of this file and display them:

```python
# Reading from a file
file_name = "example.txt"

try:
    with open(file_name, "r") as file:
        content = file.read()
        print(content)
except FileNotFoundError:
    print(f"File '{file_name}' not found.")
```

2. Writing to a File:
Now, let's create a new file and write some content into it:

```python
# Writing to a file
file_name = "new_file.txt"

content_to_write = "This is some content that we want to write to the file."

try:
    with open(file_name, "w") as file:
        file.write(content_to_write)
    print(f"Content written to '{file_name}' successfully.")
except Exception as e:
    print(f"An error occurred: {str(e)}")
```

3. Appending to a File:
Appending allows you to add content to an existing file without overwriting its contents:

```python
# Appending to a file
file_name = "existing_file.txt"

content_to_append = "\nThis line will be appended to the file."

try:
    with open(file_name, "a") as file:
        file.write(content_to_append)
    print(f"Content appended to '{file_name}' successfully.")
except Exception as e:
    print(f"An error occurred: {str(e)}")
```

4. Reading Line by Line:
You can also read the file line by line using a loop:

```python
# Reading file line by line
file_name = "example.txt"

try:
    with open(file_name, "r") as file:
        for line in file:
            print(line.strip())  # strip() removes the newline characters
except FileNotFoundError:
    print(f"File '{file_name}' not found.")
```

Remember to handle exceptions properly while working with files, as shown in the examples above, to ensure your code remains robust.

Please make sure you have the appropriate file permissions to read from or write to the files in your directory. 
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