Basic application code

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from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return 'Hello, World!'

Routing

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@app.route(...)

Browsers automatically append a trailingslash (canonical URL).
If the route does not end with a trailing slash, a client accessing a canonical URL will receive a 404

POST requests

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@app.route(..., methods=["POST"])
def func():
  ...

#Variable Rules

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@app.route('/path/<VARIABLE_NAME>')
def someFunc(<VARIABLE_NAME>):
    return <VARIABLE_NAME>

@app.route(‘/path/’) def someFunc(): return 

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|Converter Type|Description|
|:--|:--|
string|(default) accepts any text without a slash
int|accepts positive integers
float|accepts positive floating point values
path|like string but also accepts slashes
uuid|accepts UUID strings

# Static Files
```python3
url_for('static', filename=<FILENAME>)

Store files in the static directory

Template Rendering

Templating uses Jinja2 as the processor Store templates in the templates directory

Accessing request data

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from flask import request

POST -> request.form[<KEY>]  
REQ  -> requests.args.get(<KEY>, <DEFAULT>)
FILE -> request.files[<KEY>]

Cookies

Set cookies -> <response>.set_cookie(<KEY>, <VALUE>)
Get cookies -> request.cookies.get(<KEY>)

Redirect

flask.redirect(<PATH>)

Errors

flask.abort(<STATUS_CODE>)

Error Handlers

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@app.errorhandler(<STATUS_CODE>)
def func(error):
  return ..., <STATUS_CODE>)

Session Management

``flask.session Session is stored INSIDE the client’s cookies (encrypted with the secret key)

$ python -c ‘import os; print(os.urandom(16))’ b’_5#y2L”F4Q8z\n\xec]/’

Message flashing

Putting data created from one response into another request (ie to write ‘successful login’)

Deferred Request Callbacks

We can write functions that will execute before (and) after a was reached

Apply the @<app>.before_request decorator onto the function

Apply the flask.after_this_request decorator onto a function that is defined inside