Python Flask solves cross-domain problems

python video tutorial column introduces Python Flask to solve cross-domain problems.

Directory of series of articles

Table of Contents

• Directory of series of articles
• Preface
• Usage steps
  • 1. Import the library
  • 2. Configuration
    • 1. Use the CORS function to configure global routing
    • 2. Use @cross_origin to configure single-line routing
  • Configuration parameter description
##Summary
• Reference

---

Preface

Holy crap, it’s cross-domain again

Usage steps

1. Import the library

pip install flask-cors复制代码

2. Configuration

flask-cors has two usages, one is for global use, and the other is for specified routing

1. Use the

CORS function Configure global routing

from flask import Flask, requestfrom flask_cors import CORS

app = Flask(__name__)
CORS(app, supports_credentials=True)复制代码

CORS provides some parameters to help us customize the operation.

We can configure commonly used

origins, methods, allow_headers, supports_credentials

All configuration items are as follows:

:param resources:
    The series of regular expression and (optionally) associated CORS
    options to be applied to the given resource path.

    If the argument is a dictionary, it's keys must be regular expressions,
    and the values must be a dictionary of kwargs, identical to the kwargs
    of this function.

    If the argument is a list, it is expected to be a list of regular
    expressions, for which the app-wide configured options are applied.

    If the argument is a string, it is expected to be a regular expression
    for which the app-wide configured options are applied.

    Default : Match all and apply app-level configuration

:type resources: dict, iterable or string

:param origins:
    The origin, or list of origins to allow requests from.
    The origin(s) may be regular expressions, case-sensitive strings,
    or else an asterisk

    Default : '*'
:type origins: list, string or regex

:param methods:
    The method or list of methods which the allowed origins are allowed to
    access for non-simple requests.

    Default : [GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]
:type methods: list or string

:param expose_headers:
    The header or list which are safe to expose to the API of a CORS API
    specification.

    Default : None
:type expose_headers: list or string

:param allow_headers:
    The header or list of header field names which can be used when this
    resource is accessed by allowed origins. The header(s) may be regular
    expressions, case-sensitive strings, or else an asterisk.

    Default : '*', allow all headers
:type allow_headers: list, string or regex

:param supports_credentials:
    Allows users to make authenticated requests. If true, injects the
    `Access-Control-Allow-Credentials` header in responses. This allows
    cookies and credentials to be submitted across domains.

    :note: This option cannot be used in conjuction with a '*' origin

    Default : False
:type supports_credentials: bool

:param max_age:
    The maximum time for which this CORS request maybe cached. This value
    is set as the `Access-Control-Max-Age` header.

    Default : None
:type max_age: timedelta, integer, string or None

:param send_wildcard: If True, and the origins parameter is `*`, a wildcard
    `Access-Control-Allow-Origin` header is sent, rather than the
    request's `Origin` header.

    Default : False
:type send_wildcard: bool

:param vary_header:
    If True, the header Vary: Origin will be returned as per the W3
    implementation guidelines.

    Setting this header when the `Access-Control-Allow-Origin` is
    dynamically generated (e.g. when there is more than one allowed
    origin, and an Origin than '*' is returned) informs CDNs and other
    caches that the CORS headers are dynamic, and cannot be cached.

    If False, the Vary header will never be injected or altered.

    Default : True
:type vary_header: bool复制代码

2. Use

@cross_origin to configure single-line routing

from flask import Flask, requestfrom flask_cors import cross_origin

app = Flask(__name__)@app.route('/')@cross_origin(supports_credentials=True)def hello():
    name = request.args.get("name", "World")    return f'Hello, {name}!'复制代码

where

cross_origin and CORS provides some essentially the same parameters.

We can configure commonly used

origins, methods, allow_headers, supports_credentials

All configuration items are as follows:

:param origins:
    The origin, or list of origins to allow requests from.
    The origin(s) may be regular expressions, case-sensitive strings,
    or else an asterisk

    Default : '*'
:type origins: list, string or regex

:param methods:
    The method or list of methods which the allowed origins are allowed to
    access for non-simple requests.

    Default : [GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]
:type methods: list or string

:param expose_headers:
    The header or list which are safe to expose to the API of a CORS API
    specification.

    Default : None
:type expose_headers: list or string

:param allow_headers:
    The header or list of header field names which can be used when this
    resource is accessed by allowed origins. The header(s) may be regular
    expressions, case-sensitive strings, or else an asterisk.

    Default : '*', allow all headers
:type allow_headers: list, string or regex

:param supports_credentials:
    Allows users to make authenticated requests. If true, injects the
    `Access-Control-Allow-Credentials` header in responses. This allows
    cookies and credentials to be submitted across domains.

    :note: This option cannot be used in conjuction with a '*' origin

    Default : False
:type supports_credentials: bool

:param max_age:
    The maximum time for which this CORS request maybe cached. This value
    is set as the `Access-Control-Max-Age` header.

    Default : None
:type max_age: timedelta, integer, string or None

:param send_wildcard: If True, and the origins parameter is `*`, a wildcard
    `Access-Control-Allow-Origin` header is sent, rather than the
    request's `Origin` header.

    Default : False
:type send_wildcard: bool

:param vary_header:
    If True, the header Vary: Origin will be returned as per the W3
    implementation guidelines.

    Setting this header when the `Access-Control-Allow-Origin` is
    dynamically generated (e.g. when there is more than one allowed
    origin, and an Origin than '*' is returned) informs CDNs and other
    caches that the CORS headers are dynamic, and cannot be cached.

    If False, the Vary header will never be injected or altered.

    Default : True
:type vary_header: bool

:param automatic_options:
    Only applies to the `cross_origin` decorator. If True, Flask-CORS will
    override Flask's default OPTIONS handling to return CORS headers for
    OPTIONS requests.

    Default : True
:type automatic_options: bool复制代码

Configuration parameter description

##Parameterresourcesoriginsmethodsexpose_headersallow_headers##supports_credentialsBoolean valueAccess-Control- Allow-CredentialsFalseWhether to allow requests to send cookiestimedelta, integer, string In the cross-domain configuration of flask, we can use flask-cors

Type	Head	Default	Description
Dictionary, iterator or string	None	All	Configure routing interfaces that allow cross-domain routing
List, string or regular expression	Access-Control-Allow-Origin	*	Configure origins that allow cross-domain access
List, string	Access-Control-Allow-Methods	[GET, HEAD, POST, OPTIONS, PUT, PATCH, DELETE]	Configure cross-domain support Request method
List, string	Access-Control-Expose-Headers	None	Customize request response Head information
List, string or regular expression	Access-Control-Request-Headers	*	Configure cross-domain request headers
				##max_age
Access-Control-Max-Age	None	Valid duration of preflight request		##Summary

for configuration, where

CORS function

is used for global configuration, and

@cross_origin is used to implement Configuration of specific routes. More related free learning recommendations:

python video tutorial

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