Validate request arguments, Including Cross Field, Cross Struct

filter, flask, request, translation, validation
pip install pre-request==2.1.5


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This framework is designed to validate request params for Flask web framework.

It has the following unique features:

  • Cross Field and Cross Struct validations
  • Array and Map diving, which allows any or all levels of a multidimensional field to be validated
  • Customizable error response


you can simply install it by PyPi:

pip install pre-request


pre-request manual could be found at:

A Simple Example

This is very easy to use pre-request in your project

from flask import Flask

from pre_request import pre, Rule

app = Flask(__name__)

args = {
   "userId": Rule(type=int, required=True)

def hello_world(params):
   from flask import g
   return str(params == g.params)

what happened in this code ?

  1. Use pre-request library to import a global object pre
  2. Define request params rule, e.g. userId must be type of int and required
  3. Use @pre.catch(req_params) to filter input value
  4. Use ~flask.g or def hello_world(params) to get formatted input value。

Complex Example

We use a very complex example to show the powerful of this framework. Otherwise you can find amount of examples at:

from flask import Flask
from pre_request import pre, Rule

args = {
    "userFirst": {
        "userId": Rule(type=int, required=False),
        "socialInfo": {
            "gender": Rule(type=int, enum=[1, 2], default=1),
            "age": Rule(type=int, gte=18, lt=80),
            "country": Rule(required=True, deep=False)
    "userSecond": {
        "userId": Rule(type=int, required=False, neq_key="userFirst.userId"),
        "friends": Rule(type=dict, required=True, multi=True, structure={
            "userId": Rule(type=int, required=True, dest="user_id"),
            "userName": Rule(type=str, required=True, dest="user_name")

app = Flask(__name__)
app.config["TESTING"] = True
client = app.test_client()

@app.route("/structure", methods=["GET", "POST"])
def structure_handler(params):
    return str(params)

if __name__ == "__main__":
    resp = app.test_client().post("/structure", json={
        "userFirst": {
            "userId": "13",
            "socialInfo": {
                "age": 20,
        "userSecond": {
            "userId": 14,
            "friends": [
                    "userId": 13,
                    "userName": "Trump"
        "country": "CN",
        "userFirst.socialInfo.gender": 1


Use parse

We can use function pre.parse instead of decorator @pre.catch()

args = {
    "params": Rule(email=True)

def params_value_error(e):
    return pre.fmt_resp(e)

def example_handler():
    rst = pre.parse(args)
    return str(rst)


How to make a contribution to Pre-request, see the contributing.


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