📝 Add docs for debugging

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Sebastián Ramírez 2019-03-02 17:40:01 +04:00
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import uvicorn
from fastapi import FastAPI
app = FastAPI()
@app.get("/")
def root():
a = "a"
b = "b" + a
return {"hello world": b}
if __name__ == "__main__":
uvicorn.run(app, host="0.0.0.0", port=8000)

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You can connect the debugger in your editor, for example with Visual Studio Code or PyCharm.
## Call `uvicorn`
In your FastAPI application, import and run `uvicorn` directly:
```Python hl_lines="1 15"
{!./src/debugging/tutorial001.py!}
```
### About `__name__ == "__main__"`
The main purpose of the `__name__ == "__main__"` is to have some code that is executed when your file is called with:
```bash
python myapp.py
```
but is not called when another file imports it, like in:
```Python
from myapp import app
```
#### More details
Let's say your file is named `myapp.py`.
If you run it with:
```bash
python myapp.py
```
then the internal variable `__name__` in your file, created automatically by Python, will have as value the string `"__main__"`.
So, the section:
```Python
uvicorn.run(app, host="0.0.0.0", port=8000)
```
will run.
---
This won't happen if you import that module (file).
So, if you have another file `importer.py` with:
```Python
from myapp import app
# Some more code
```
in that case, the automatic variable inside of `myapp.py` will not have the variable `__name__` with a value of `"__main__"`.
So, the line:
```Python
uvicorn.run(app, host="0.0.0.0", port=8000)
```
will not be executed.
## Run your code with your debugger
Because you are running the Uvicorn server directly from your code, you can call your Python program (your FastAPI application) directly form the debugger.
---
For example, in Visual Studio Code, you can:
* Go to the "Debug" panel.
* "Add configuration...".
* Select "Python"
* Run the debugger with the option "`Python: Current File (Integrated Terminal)`".
It will then start the server with your **FastAPI** code, stop at your breakpoints, etc.
Here's how it might look:
<img src="/img/tutorial/debugging/image01.png">

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@ -62,6 +62,7 @@ nav:
- Sub Applications - Behind a Proxy: 'tutorial/sub-applications-proxy.md' - Sub Applications - Behind a Proxy: 'tutorial/sub-applications-proxy.md'
- Application Configuration: 'tutorial/application-configuration.md' - Application Configuration: 'tutorial/application-configuration.md'
- GraphQL: 'tutorial/graphql.md' - GraphQL: 'tutorial/graphql.md'
- Debugging: 'tutorial/debugging.md'
- Concurrency and async / await: 'async.md' - Concurrency and async / await: 'async.md'
- Deployment: 'deployment.md' - Deployment: 'deployment.md'
- Project Generation - Template: 'project-generation.md' - Project Generation - Template: 'project-generation.md'