Processing requests

demand

How can the data be correctly fetched when the data requested by the client needs to be read in view writing?

The data carried by the request may appear in different locations in the HTTP message, and different methods need to be used to obtain parameters.

1. URL path parameters (dynamic routing)

For example, there is an interface address requesting access to / users/123, where 123 is actually a specific request parameter, indicating the information of user 123. How to extract 123 data from the url?

Unlike Django's direct way of writing regular expressions when defining routes, Flask adopts converter syntax:

@app.route('/users/<user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)

Example code:

from flask import Flask

app = Flask(__name__)


@app.route('/users/<user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)


if __name__ == '__main__':
    app.run()

Operation effect:

The < > here is a converter, which defaults to string type, that is, the data at this location is matched in string format, and the string is used as the data type and user_id is the parameter name passed into the view.

Flask also provides other types of converters

DEFAULT_CONVERTERS = {
    'default':          UnicodeConverter,
    'string':           UnicodeConverter,
    'any':              AnyConverter,
    'path':             PathConverter,
    'int':              IntegerConverter,
    'float':            FloatConverter,
    'uuid':             UUIDConverter,
}

Using the above example to match data with integer, you can use it as follows:

@app.route('/users/<int:user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)


@app.route('/users/<int(min=1):user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)

Example code 1:

from flask import Flask

app = Flask(__name__)


@app.route('/users/<int:user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)


if __name__ == '__main__':
    app.run()

Operation effect:

Example code 2:

from flask import Flask

app = Flask(__name__)


@app.route('/users/<int(min=3):user_id>')
def user_info(user_id):
    print(type(user_id))
    return 'hello user {}'.format(user_id)


if __name__ == '__main__':
    app.run()

Operation effect:

Custom converter

If a match is needed, extract / SMS_ For the mobile phone number data in codes / 18512345678, the built-in converter in Flask cannot meet the requirements. At this time, you need to customize the converter.

Definition method

There are three steps to customize the converter

1. Create a converter class and save the regular expression when matching

   from werkzeug.routing import BaseConverter
   
   class MobileConverter(BaseConverter):
       """
       Mobile number format
       """
       regex = r'1[3-9]\d{9}'
   

   • Note that the regex name is fixed

2. Inform the flash application of the custom converter

   app = Flask(__name__)
   
   # Add a custom converter to the converter dictionary and specify the name of the converter when it is used: mobile
   app.url_map.converters['mobile'] = MobileConverter
   

3. Define where the converter is used

   @app.route('/sms_codes/<mobile:mob_num>')
   def send_sms_code(mob_num):
       return 'send sms code to {}'.format(mob_num)
   

Example code:

from flask import Flask
from werkzeug.routing import BaseConverter


class MobileConverter(BaseConverter):
    """Mobile number format"""
    regex = r'1[3-9]\d{9}'


app = Flask(__name__)

# Add a custom converter to the converter dictionary and specify the name of the converter when it is used: mobile
app.url_map.converters['mobile'] = MobileConverter


@app.route('/sms_codes/<mobile:mob_num>')
def send_code(mob_num):
    return 'send sms code to {}'.format(mob_num)


if __name__ == '__main__':
    app.run()

Operation effect:

2. Other parameters

If you want to get the parameters passed elsewhere, you can read them through the request object provided by Flask.

Parameters in different locations are stored in different attributes of request

attribute	explain	type
data	Record the requested data and convert it to a string	*
form	Record the form data in the request	MultiDict
args	Record the query parameters in the request	MultiDict
cookies	Record cookie information in the request	Dict
headers	Record the message header in the request	EnvironHeaders
method	Record the HTTP method used by the request	GET/POST
url	Record the URL address of the request	string
files	Record the file requested to be uploaded	*

For example, would you like to get the request / articles? channel_ Channel in id = 1_ The parameter ID can be used as follows:

from flask import request

@app.route('/articles')
def get_articles():
    channel_id = request.args.get('channel_id')
    return 'you wanna get articles of channel {}'.format(channel_id)

Example code:

from flask import Flask, request

app = Flask(__name__)


@app.route('/articles')
def get_articles():
    channel_id = request.args.get('channel_id')
    return 'you wanna get articles of channel {}'.format(channel_id)


if __name__ == '__main__':
    app.run()

Operation effect:

Upload pictures

The client uploads the picture to the server and saves it to the server

from flask import request

@app.route('/upload', methods=['POST'])
def upload_file():
    f = request.files['pic']
    # with open('./demo.png', 'wb') as new_file:
    #     new_file.write(f.read())
    f.save('./demo.png')
    return 'ok'

Example code:

from flask import Flask, request

app = Flask(__name__)


@app.route('/upload', methods=['POST'])
def upload_file():
    f = request.files['pic']
    # with open('./demo.png', 'wb') as new_file:
    #     new_file.write(f.read())
    f.save('./demo.png')
    return 'ok'


if __name__ == '__main__':
    app.run()

[the effect of with open is the same as that of f.save, and f.save is a encapsulated method]

Post man upload picture test: