# Lab 12: Find the most frequent words in a text read from a file

Write a Python program to compute the most frequently used words from the text file.

## Example

```
python frequent.py file1.txt -> file1.txt, "the" 12
```

## Pre-Lab Questions

1. Distinguish between syntax errors (compile time) and exceptions (run time).
2. There may not exist a file with the user provided filename(s) on the command line. In that case, a built-in [OS-level exception](https://docs.python.org/3/library/exceptions.html#os-exceptions) will be `raise`d when the program is executed. Write a Python function `open_file(filename)` that handles the appropriate exception (<https://docs.python.org/3/library/exceptions.html#FileNotFoundError>) and re-`raise` the exception (allowing a caller to handle the exception as well). To help you get started, the basic code for `open_file` is already provided below.

   ```python
   def open_file(filename):
       file = open(filename, 'r')
   	return file
   ```
3. When such a function `open_file()`is called with the appropriate argument, it is recommended coding practice to have exception handling code in the calling code or function to handle `OS_exceptions`. What would that exception handling code be for handling the specific exception which was raised in the previous question?
4. What is the difference between a text file and a binary file?
5. Imagine that the user specifies a filename, and a file exists with the same name but it happens to be a binary file and not a text file. If the program tries to read a binary file when it is expecting a text file, other exceptions will occur. What additional exception handling code would you add to handle **all other types** of exceptions that may arise, including the binary file scenario?

## Post-lab Questions

1. How can you compare whether two files are equal in Python?

   ```
   python -c "print open('f0.txt', 'rb').read() == open('f1.txt', 'rb').read()"
   ```

## Related Material

<http://programmingzen.com/use-python-to-detect-the-most-frequent-words-in-a-file/>

<http://mcsp.wartburg.edu/zelle/python/sigcse-workshop/mgp00047.html>


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