🔒 I dont understand flasks in python

[jovial aurora]

Can someone explain this code. I dont understand, how the app.route, triggers the function say_hello, how are they related? or linked?

[glossy bobcat]

@jovial aurora

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[winter arch]

The app.route decorator registers the say_hello function in the app's mapping which says what functions to run for what URLs.

When someone fetches the URL http://yoursite/hello the flask app then knows to call the hello function to obtain the text to return in the web page.

[jovial aurora]

what i dont understand, is how the say_hello function runs when someone visits the site

is it because its below the @app.route("/hello")

[winter arch]

Yes.

Do you know what a decorator is?

[jovial aurora]

Not really

but someome showed me this

Which kinda makes sense assuming its actually the same

[winter arch]

It is. A decorator is a function which gets applied to another function. Sometimes it does something with the function, like flask does here, then returns the originl function. Sometimes it defines a new function which will wrap the original function, and returns the wrapper function.

[placid socket]

thats what the decoration is

[winter arch]

So in this case, the code:

@app.route("/hello")
def say_hello():

calls app.route("/hello")(say_hello)
hich seems round about, but sane.

It does this to record say_hello against a table of URLs, in this case for the /hello URL.

The app.route decorator will return say_hello unchanged. But it will have recorded it in the registry of functions-which-serve-URLs.

[placid socket]

@app.route("/hello")
def index():
  return "hello"

# same as
def index():
  return "hello"
app.route("\hello")(index) ```

[jovial aurora]

so could you describe a decorator, as do this thing, but do this other thing first? or it like for example modifing somthing

[jovial aurora]

in what other way, or concept, could @app.route, etc, be explained , like is they a simpler like more basic python version of this? or is this just as it is

[placid socket]

the "@" simbol will basically apply that

[winter arch]

It's more like this:

def app_route(url_path, func):
    flask.url_mapping[url_path] = func
    return func

Ignoring the complexity, this is what's happening - the say_hello function and the URL /hello are being passed to a function (the decorator) which records the function in a table. Then returns the original function.

So when the @ is used, which means:

say_hello = app.route("/hello")(say_hello)

it's defining say_hello as itself. But during the decoration it gets recorded in flask's table.

[jovial aurora]

i give up rn, im going to come back to thsi later, my brain feels fogged, thank you tho, you can explain anything else if there is

[placid socket]

having a good rest helps everyone

[glossy bobcat]

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