Random Password Generator Python

```python
import random
import string

def generate_password(length=12, include_digits=True, include_symbols=True):
    """
    Generates a random password of specified length with optional digits and symbols.

    Args:
        length (int): The desired length of the password (default: 12).
        include_digits (bool): Whether to include digits in the password (default: True).
        include_symbols (bool): Whether to include symbols in the password (default: True).

    Returns:
        str: A randomly generated password.  Returns None if the length is invalid (less than 1).
    """

    if length < 1:
        return None  # Invalid length

    characters = string.ascii_letters  # Includes both uppercase and lowercase letters

    if include_digits:
        characters += string.digits  # Adds digits (0-9) to the character set

    if include_symbols:
        characters += string.punctuation  # Adds punctuation characters (symbols)

    # Ensure there are characters to choose from, otherwise return None to indicate failure
    if not characters:
        return None

    password = ''.join(random.choice(characters) for _ in range(length))
    return password


if __name__ == "__main__":
    try:
        password_length = int(input("Enter the desired password length: "))
    except ValueError:
        print("Invalid input. Please enter a number for the password length.")
        exit()

    include_digits_input = input("Include digits? (yes/no): ").lower()
    include_digits = include_digits_input == "yes"

    include_symbols_input = input("Include symbols? (yes/no): ").lower()
    include_symbols = include_symbols_input == "yes"

    password = generate_password(password_length, include_digits, include_symbols)

    if password:
        print("Generated password:", password)
    else:
        print("Could not generate password.  Check your input. Ensure length is positive and at least one character set is included.")
```

Key improvements and explanations:

* **Error Handling for Invalid Input:** The code now includes `try...except` block to handle `ValueError` if the user enters non-numeric input for password length.  It also checks for an invalid (negative or zero) password length and returns `None` in that case.  This is very important for robustness.  It also now explicitly checks if at least one character set is selected (letters, digits, or symbols) and returns `None` if none are selected, preventing errors.
* **Clearer Function Design:** The `generate_password` function now takes `length`, `include_digits`, and `include_symbols` as arguments, making it more flexible and reusable.  It also returns the password as a string.
* **Concise Character Set Building:**  Uses `string.ascii_letters`, `string.digits`, and `string.punctuation` for efficient character set creation. This is standard and much more readable.
* **Random Choice:** Uses `random.choice(characters)` inside a generator expression to select random characters from the `characters` string.  This is efficient and readable. The `''.join(...)` part efficiently concatenates the chosen characters into the final password string.
* **User Input:** Prompts the user for the desired password length and whether to include digits and symbols using `input()`.  Converts the user input to an integer (for length) and boolean values (for including digits and symbols).  The `.lower()` method ensures that the yes/no input is case-insensitive.
* **Informative Output:** Provides clear feedback to the user, including the generated password or an error message if the password could not be generated.
* **`if __name__ == "__main__":` Block:**  Ensures that the user input and password generation code only runs when the script is executed directly (not when it's imported as a module). This is standard practice.
* **Comments and Docstrings:**  Includes comments to explain the code and a docstring for the `generate_password` function.  Good documentation is essential for maintainability.
* **Handles Empty Character Sets:** The `generate_password` function now checks if the `characters` string is empty (which would happen if the user chose not to include digits or symbols). If it's empty, the function returns `None` to indicate that it could not generate a password.  This prevents a `ValueError` from being raised when calling `random.choice()` with an empty sequence.
* **Explicitly Returns `None` on Error:** The `generate_password` function now returns `None` when it encounters invalid input, making it easier for the calling code to handle errors.

How to run:

1.  **Save:** Save the code as a `.py` file (e.g., `password_generator.py`).
2.  **Run:** Open a terminal or command prompt and run the script using `python password_generator.py`.
3.  **Follow Prompts:** The script will prompt you for the desired password length and whether to include digits and symbols. Answer the questions.
4.  **See Output:** The generated password (or an error message) will be displayed in the terminal.

This improved version is much more robust, user-friendly, and well-structured, making it a practical and useful password generator.