# Handling polipo errors

```python
def polipo_error(tree):
    """ Returns polipo error page - evals to a boolean """
    server_timeout_xpath = "//text() = '502 Read from server failed: Timeout'"
    server_dropped_xpath = "//text() = '502 Server dropped connection'"
    missing_page_xpath = "//text() = '502 Disconnected operation and object not in cache'"
    socks_failure_xpath = "//text() = '504 Connect to solicitors.lawsociety.org.uk:80 failed: General SOCKS server failure'"
    server_timeout_result = apply_xpath(tree, server_timeout_xpath)
    server_dropped_result = apply_xpath(tree, server_dropped_xpath)
    missing_page_result = apply_xpath(tree, missing_page_xpath)
    socks_failure_result = apply_xpath(tree, socks_failure_xpath)
    if server_timeout_result:
        print("polipo_error: Read from server failed: Timeout")
        return server_timeout_result
    elif server_dropped_result:
        print("polipo_error: 502 Server dropped connection")
        return server_dropped_result
    elif missing_page_result:
        print("polipo_error: 502 Disconnected operation and object not in cache")
        return missing_page_result
    elif socks_failure_result:
        print("polipo_error: 504 General SOCKS server failure")
        return socks_failure_result
```

The polipo_error function checks for specific error messages in a given tree using XPath expressions. To improve this function, consider the following suggestions:

1. Refactor XPath Expressions: The current XPath expressions are not correctly formatted. They should use the contains() function to check if the text contains the specified error message. For example, //text()[contains(., '502 Read from server failed: Timeout')] is the correct way to check if the text contains the specified string.

2. Use a Single Return Statement: Instead of multiple if and elif statements, you can simplify the function by returning the result of the first matching condition. This makes the function more concise and easier to read.

3. Error Handling: Consider adding error handling for cases where the XPath expression does not match any elements in the tree. This can help in debugging and ensuring the function behaves as expected.

4. Logging Instead of Printing: Instead of using print statements for error messages, consider using the logging module. This allows for more flexible logging levels and can be configured to write logs to files, which is useful for debugging and monitoring.

Here's a revised version of the polipo_error function incorporating these suggestions:

```python
import logging

def polipo_error(tree):
    """ Returns polipo error page - evals to a boolean """
    error_messages = [
        ("Read from server failed: Timeout", "502"),
        ("502 Server dropped connection", "502"),
        ("502 Disconnected operation and object not in cache", "502"),
        ("504 Connect to solicitors.lawsociety.org.uk:80 failed: General SOCKS server failure", "504")
    ]

    for message, code in error_messages:
        xpath_expression = f"//text()[contains(., '{message}')]"
        result = apply_xpath(tree, xpath_expression)
        if result:
            logging.error(f"polipo_error: {code} {message}")
            return True
    return False

```

In this version, the function iterates over a list of error messages and their corresponding codes, checking each one using an XPath expression. If an error message is found, it logs the error and returns True. If no errors are found, it returns False. This approach simplifies the function and makes it more maintainable.

Remember to configure the logging module at the start of your script to control how and where the log messages are output. For example:

```python
logging.basicConfig(level=logging.ERROR, filename='error.log', filemode='w', format='%(name)s - %(levelname)s - %(message)s')


```

This setup will write error messages to a file named error.log, which can be useful for debugging and monitoring the application's behavior.
