Flask - request.args.getlist - 只能读取一次？答案

【问题标题】：Flask - request.args.getlist - Can only be read once?Flask - request.args.getlist - 只能读取一次？
【发布时间】：2021-01-05 21:06:20
【问题描述】：

在我的 Flask 应用程序中，我使用如下参数重定向到另一个页面：

return redirect(url_for("edit.editFunction", plants=thisPlant))

然后，在另一个文件中，我正在使用这些行读取该参数：

    # Get arguments from url_for in administration
    thisPlant = request.args.getlist("plants")
    print(thisPlant)

    # Get ID on edit plant
    plant_id = thisPlant[0]
    print(plant_id)

到目前为止，这在我的控制台中返回：

['1', 'aa', '11', '11', 'https://i.ibb.co/QNJnLR8/empty.png', 'aa', '1']
1

但是当我想在同一个文件上使用 post 方法时，我得到了这个：

    plant_id = thisPlant[0]
IndexError: list index out of range

怎么可能？我应该阅读1 有人能看出我的错误吗？

这是我使用此变量的完整文件：

import sqlite3
import traceback
import sys
import re
import os

from flask import Blueprint, render_template, redirect, session, request, flash, get_flashed_messages
from application import getUserName, getUserPicture, login_required, confirmed_required, getUserRole, role_required, uploadPicture
from werkzeug.utils import secure_filename

# Set Blueprints
edit = Blueprint('edit', __name__,)

@edit.route("/edit", methods=["GET", "POST"])
@login_required
@confirmed_required
@role_required
def editFunction():    

    # Force flash() to get the messages on the same page as the redirect.
    get_flashed_messages()

    if request.method == "POST":

        # Get variables
        plant_id = request.form.get("plant_id")
        name = request.form.get("name")
        stock = request.form.get("stock")
        price = request.form.get("price")
        description = request.form.get("description")

        # Ensure the plant name was submitted
        if not name:
            flash("must provide plant name")
            return redirect("/edit")

        # Ensure the plant name fits server-side
        if not re.search("^[a-zA-Z0-9]{1,50}$", name):
            flash("Invalid plant name")
            return redirect("/edit")

        # Ensure the plant stock was submitted
        if not stock:
            flash("must provide plant stock")
            return redirect("/edit")

        # Ensure the plant stock fits server-side
        if not re.search("^[0-9]+$", stock):
            flash("Invalid plant stock")
            return redirect("/edit")

        # Ensure the plant price was submitted
        if not stock:
            flash("must provide plant price")
            return redirect("/edit")

        # Ensure the plant price fits server-side
        if not re.search("^[0-9]+$", stock):
            flash("Invalid plant price")
            return redirect("/edit")

        # Ensure the plant description was submitted
        if not description:
            flash("must provide plant description")
            return redirect("/edit")

        # Ensure the plant description fits server-side
        if not re.search("^(?!;).+", description):
            flash("Invalid plant description")
            return redirect("/edit")

        # Check show bool status
        show = "show" in request.form


        # Update plant name, stock, price, description and show status into the table
        try:

            sqliteConnection = sqlite3.connect("database.db")
            cursor = sqliteConnection.cursor()

            cursor.execute("UPDATE plants SET name=:name, stock=:stock, price=:price, description=:description, show=:show WHERE id=:plant_id;", {"name": name, "stock": stock, "price": price, "description": description, "show": show, "plant_id": plant_id})
            sqliteConnection.commit()

            cursor.close()

        except sqlite3.Error as error:
        
            print("Failed to read data from sqlite table", error)
            print("Exception class is: ", error.__class__)
            print("Exception is", error.args)

            print('Printing detailed SQLite exception traceback: ')
            exc_type, exc_value, exc_tb = sys.exc_info()
            print(traceback.format_exception(exc_type, exc_value, exc_tb))

        finally:

            if (sqliteConnection):
                sqliteConnection.close()

        # Save, upload and delete picture file
        file = request.files["picture"]

        if file and file.filename:

            filename = secure_filename(file.filename)
            file.save(os.path.join("./static", filename))
            upload = uploadPicture("./static/" + filename)
            os.remove("./static/" + filename)

            # Update database with new image url 
            try:

                sqliteConnection = sqlite3.connect("database.db")
                cursor = sqliteConnection.cursor()
                
                cursor.execute("UPDATE plants SET picture=:picture WHERE name=:name;", {"picture": upload, "name": name})
                sqliteConnection.commit()

                cursor.close()

            except sqlite3.Error as error:
            
                print("Failed to read data from sqlite table", error)
                print("Exception class is: ", error.__class__)
                print("Exception is", error.args)

                print('Printing detailed SQLite exception traceback: ')
                exc_type, exc_value, exc_tb = sys.exc_info()
                print(traceback.format_exception(exc_type, exc_value, exc_tb))

            finally:

                if (sqliteConnection):
                    sqliteConnection.close()

        flash("Plant edited")
        return redirect("/administration")


    else:
        # Get arguments from url_for in administration
        thisPlant = request.args.getlist("plants")
    
        return render_template("edit.html", name=getUserName(), picture=getUserPicture(), role=getUserRole(), plants=thisPlant)

这是完整的控制台输出：

127.0.0.1 - - [05/Jan/2021 22:20:44] "GET /administration HTTP/1.1" 200 -
127.0.0.1 - - [05/Jan/2021 22:20:44] "GET /static/styles.css HTTP/1.1" 200 -
127.0.0.1 - - [05/Jan/2021 22:20:45] "POST /administration HTTP/1.1" 302 -
['1', 'aa', '11', '11', 'https://i.ibb.co/QNJnLR8/empty.png', 'aa', '1']
1
127.0.0.1 - - [05/Jan/2021 22:20:45] "GET /edit?plants=1&plants=aa&plants=11&plants=11&plants=https%3A%2F%2Fi.ibb.co%2FQNJnLR8%2Fempty.png&plants=aa&plants=1 HTTP/1.1" 200 -
127.0.0.1 - - [05/Jan/2021 22:20:45] "GET /static/styles.css HTTP/1.1" 200 -
[]
[2021-01-05 22:20:53,655] ERROR in app: Exception on /edit [POST]
Traceback (most recent call last):
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 94, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 109, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 124, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/routes/edit.py", line 28, in editFunction
    plant_id = thisPlant[0]
IndexError: list index out of range
127.0.0.1 - - [05/Jan/2021 22:20:53] "POST /edit HTTP/1.1" 500 -
Error on request:
Traceback (most recent call last):
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 94, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 109, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/application.py", line 124, in decorated_function
    return f(*args, **kwargs)
  File "/home/benoit/Documents/CrazyPlantCrew/routes/edit.py", line 28, in editFunction
    plant_id = thisPlant[0]
IndexError: list index out of range

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/werkzeug/serving.py", line 304, in run_wsgi
    execute(self.server.app)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/werkzeug/serving.py", line 292, in execute
    application_iter = app(environ, start_response)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1881, in handle_exception
    return self.finalize_request(server_error, from_error_handler=True)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 1968, in finalize_request
    response = self.make_response(rv)
  File "/home/benoit/Documents/CrazyPlantCrew/venv/lib/python3.8/site-packages/flask/app.py", line 2097, in make_response
    raise TypeError(
TypeError: The view function did not return a valid response. The function either returned None or ended without a return statement.

编辑：添加表单

{% extends "layout.html" %}

{% block title %}
    Edit
{% endblock %}

{% block navigation %}
    {% if role == "admin" %}
        <li><a href="/administration">Administration</a></li>
        <li><a href="/communication">Update blog</a></li>
        <li><a href="/newsletter">Send newsletter</a></li>
    {% endif %}
{% endblock %}

{% block main %}
        <form action="/edit" method="post" enctype="multipart/form-data">
            <div>
                <input type='hidden' name='plant_id' value='{{ plants[0]}}'>
            </div>
            <div>
                <input id="name" autocomplete="off" autofocus class="form-control" name="name" placeholder="Name" type="text" value="{{ plants[1] }}">
            </div>
            <br>
            <div>
                <input id="stock" autocomplete="off" autofocus class="form-control" name="stock" placeholder="Stock" type="number" min="0" value="{{ plants[2] }}">
            </div>
            <br>
            <div>
                <input id="price" autocomplete="off" autofocus class="form-control" name="price" placeholder="Price" type="number" min="0" value="{{ plants[3] }}">
            </div>
            <br>
            <div>
                <textarea id="description" autocomplete="off" autofocus class="form-control" name="description" placeholder=" Description" type="text" cols="100" rows="10">{{ plants[5] }}</textarea>
            </div>
            <br>
            <div>
                <input type="file" id="picture" name="picture">
            </div>
            <br>
            <div>
                <input type="checkbox" id="show" name="show" value="show" checked="{{ plants[6] }}">
                <label for="show"> Show?</label><br>
            </div>
            <br>
            <div>
                <button id="submit" type="submit" name="submit" value="submit">Save.</button>
            </div>
            <br>
            <div>
                <a href="/administration">Back</a>
            </div>
        </form>
{% endblock %}

EDIT2：为我的代码添加解决方案 - 非常感谢 v25！

【问题讨论】：

标签： flask python-3.8 werkzeug url-for

【解决方案1】：

如果我没看错的话……

request.args.getlist 只抓取作为 URL 参数发布的数据，因此在 POST 请求期间尝试访问 plants[0] 时会出现 KeyError。注意在服务器日志中，print(thisPlant) 在 POST 请求期间给出了一个空列表：[]

似乎您只需要重组该路由，因此有问题的行仅在 GET 请求中执行。

类似：


def editFunction():    

    # Force flash() to get the messages on the same page as the redirect.
    get_flashed_messages()

    if request.method = 'GET':
        # Get arguments from url_for in administration
        thisPlant = request.args.getlist("plants")
        print(thisPlant)

        # Get ID on edit plant
        plant_id = thisPlant[0]
        print(plant_id)

        # Do return here, rather than in 'else' statement at bottom of file
        return render_template("edit.html", name=getUserName(), picture=getUserPicture(), role=getUserRole(), plants=thisPlant)

    elif request.method == "POST":

        # code to handle POST Request

        # ...

        flash("Plant edited")
        return redirect("/administration")

【讨论】：

问题是我需要plant_id = thisPlant[0] 的值，因为这是我需要更新的数据库中的id，所以它必须在POST 请求中。 cursor.execute("UPDATE plants SET name=:name, stock=:stock, price=:price, description=:description, show=:show WHERE id=:plant_id;", {"name": name, "stock": stock, "price": price, "description": description, "show": show, "plant_id": plant_id})我怎么不能访问这个变量？它在同一个文件中。
或者有没有其他方法可以在其他文件中访问来自return redirect(url_for("edit.editFunction", plants=thisPlant)) 的数据，而不是使用request.args.getlist("plants")？
@Benoît 您尚未包含表单的模板代码，但解决此问题的最快方法可能是在 <input type='hidden' name='plant_id' value='{{thisPlant[0]}}'> 表单中插入一个隐藏字段，然后在 post 路径中使用request.form.get("plant_id").
哦，我刚加了。
快速修复正是我所需要的。谢谢你的教导。非常感谢您的宝贵时间。