# Error FAQs 😢

* **No such file or directory: `requirements.txt`?**
  * Check that you are currently where `requirements.txt` exists. You'll know this is the case if enter `ls` (MacOS) or `dir` (Windows) into your terminal and you don't see `requirements.txt` or if you didn't spell it right in your command.
  * Or, you may be trying to do `pip3 install -r requirements.txt` inside of a correctly created and activated `venv`, but your `venv` is nested within a path that contains a folder that has a space in the name. Here's a good [**Stack Overflow post**](https://stackoverflow.com/questions/7911003/cant-install-via-pip-with-virtualenv) that explains the issue.
* **No module named 'flask\_sqlalchemy'?**
  * Make sure you've run `pip3 install -r requirements.txt` in your activated virtual environment, check out the **Virtual Environment** page if you need more help!
* **ImportError: cannot import name 'Feature' from 'setuptools'?**
  * Make sure that you have an updated `Markupsafe` version in your `requirements.txt` that you used to create virtual env: `MarkupSafe==1.1.1`
* **How to fix "KeyError: 'data'" from running test suite?**
  * This means that your backend didn't respond with a format like:`{ "success": True, "data": blah }` so try making sure that your endpoints match the API spec linked in the backend course. 
* **Postman keeps giving me an error?**
  * Make sure you are hitting the correct URL in Postman. A correct URL looks like this: `http://localhost:5000/api/posts/{id}/comments/`, while some examples of incorrect ones look like this: `http://localhost:5000/api/posts/{id}/comments`, `http://localhost:5000/posts/{id}/comments/`
  * If you are making a POST request, make sure that you are submitting a JSON request. `Body` > `Raw` > `JSON`
* **Postman 404 Not Found?**
  * Is your server running right now? Try checking your terminal. The server may stop when you make changes in your code has errors.
  * Also make sure that you have `if name == "main": app.run(host="0.0.0.0", port=5000, debug=True)` at the bottom of your `app.py`.
* **TypeError: list indices must be integers or slices, not str?**
  * You may be returning a list, and accessing string values of that list (could be yourself or the testing script), instead of accessing string values of a dictionary. Make sure your responses abide by the API spec which indicates list/dictionary return types.
* **JSONDecodeError?!**
  * `JSONDecodeError`s are among the most common in this course. It's caused when the testing script tries to parse the JSON data associated with a response (variable `res`) that does not have any JSON data associated with it. This occurs when your code in `app.py` encounters an uncaught exception and crashes before your crafted responses can be returned. To debug a `JSONDecodeError`, you need to look at which request is breaking on `res.json()` and look deeper into that route method in `app.py`. We then recommend using Postman to test that specific route.
  * Double check that you are using double quotes `"` when creating a POST body request.
  * Instead of accessing key values of a dictionary like `dict["key"]`, it's better to use `dict.get("key")` so that even if the POST request body doesn't contain the key, your code won't throw an error.
* **Test file's `base_path = f"{LOCAL_URL}/api/user"` has `SyntaxError`?**
  * Our testing script uses what's called an f string. This is only supported by Python 3.6 or higher, so make sure you're running `python3 test.py`.
* **Table X has no column named Y?**
  * Try using sqlite3 to help you debug in the terminal by

    1\) opening sqlite3 shell: `sqlite3`

    2\) loading your database file that you generate in your python code, which should show up in the same place as `app.py`: `.open <YOUR FILENAME HERE>.db`

    3\) seeing all the tables in your database file `.tables`

    4\) show what your table is made of (what the columns are): `PRAGMA table_info(<YOUR TABLE NAME HERE>);`