Work with files.

Write to File

```python # Write mode (creates new file) file = open("notes.txt", "w") file.write("Hello from San Diego!") file.close()

Better way - auto closes with open("notes.txt", "w") as file: file.write("Hello from San Diego!") ```

Read from File

```python # Read entire file with open("notes.txt", "r") as file: content = file.read() print(content)

Read line by line with open("notes.txt", "r") as file: for line in file: print(line) ```

Append to File

```python # Add to existing file with open("notes.txt", "a") as file: file.write("\nNew line added!") ```

Check if File Exists

```python import os

if os.path.exists("notes.txt"): print("File exists!") else: print("File not found") ```

Handle Errors

```python try: with open("data.txt", "r") as file: content = file.read() except FileNotFoundError: print("File doesn't exist!") ```

Remember

- Use 'with' statement - Always close files - Handle file errors