Write Files

1. Create another new function in your functions directory. Here's the signature I used:

   def write_file(working_directory: str, file_path: str, content: str) -> str:
   

2. If the file_path is outside the working_directory, return an error string like the one below. (Again, you can reuse essentially the same path validation logic that you wrote for the last two functions.)

   f'Error: Cannot write to "{file_path}" as it is outside the permitted working directory'
   

3. If the file_path points to an existing directory (this is what os.path.isdir() checks for), return an error string:

   f'Error: Cannot write to "{file_path}" as it is a directory'
   

4. Make sure that all parent directories of the file_path exist. You can use os.makedirs() with the exist_ok=True argument to create any missing directories. If the necessary directory structure already exists, this will do nothing – which is what we want.

5. Open the file at file_path in write mode ("w") and overwrite its contents with the content argument.

6. If everything succeeds, return a string with the following message:

   f'Successfully wrote to "{file_path}" ({len(content)} characters written)'
   

   It's important to return a success string so that our LLM knows that the action it took actually worked. Feedback loops, feedback loops, feedback loops!

7. Again, if any errors are raised by the standard library functions that you call, catch them and instead return a string describing the error. Always prefix error messages with Error:.

8. Create another new test module at the root of your project, test_write_file.py. It should be similar in structure to the test modules that you've written for other functions. Include the following three test cases; as always, print the results of each:

   • write_file("calculator", "lorem.txt", "wait, this isn't lorem ipsum")
   • write_file("calculator", "pkg/morelorem.txt", "lorem ipsum dolor sit amet")
   • write_file("calculator", "/tmp/temp.txt", "this should not be allowed")

Run and submit the CLI tests.

• os.path.abspath(): Get an absolute path from a relative path
• os.path.join(): Join two paths together safely (handles slashes)
• os.path.normpath(): Normalize a path (handles things like ..)
• os.path.commonpath(): Get the common sub-path shared by multiple paths
• os.path.isdir(): Check if a path points to an existing directory
• os.makedirs(): Create a directory, along with any necessary parent directories (note the optional exist_ok argument)
• os.path.dirname(): Get the parent directory of a given path
• open(): Open a file for reading or writing
• .write(): Write a string to a text file

Example of writing to a file:

with open(file_path, "w") as f:
    f.write(content)