关于在flask（flask，Python3）中保存表单数据的问题

Question

所以，我正在尝试制作一个预算应用程序，主要用于我自己的 python/flask 练习。 该应用程序适用于用户在表单中输入一个值，例如“收入”，然后将其转移到下一页。

表单数据在移动到下一个 url 时完美保存，但如果我尝试在稍后的 URL 中调用它，我会收到 BadRequestKeyError，并且页面似乎无法再找到我的表单数据。

这是代码：

from flask import Flask, render_template, request, session
from datetime import date
app = Flask(__name__)
app.secret_key = "Nash"

@app.route('/', methods=['GET'])
def entry():
    return render_template('entry.html',
                           the_title='Smith Family Budgeting')

@app.route('/income', methods=['GET'])
def income():
    session['income'] = ''
    return render_template('income.html')

@app.route('/housing', methods=['POST'])
def housing():
    if request.method == 'POST':
        session['housing'] = ''
        session['income'] = request.form["income"]
        return render_template('housing.html', the_income=session['income'])

@app.route('/transportation', methods=['POST'])
def transport():
    if request.method == 'POST':
        income = session["income"]
        session['housing'] = request.form["housing"]
        session['leftover'] = float(income) - float(session['housing'])
        return render_template('trans.html', leftover=session['leftover'])

@app.route('/food', methods=['POST'])
def food():
    if request.method == 'POST':
        session['gas'] = request.form['gas']
        session['leftover'] = int(session['leftover'] - int(session['gas']))
        return render_template('food.html', leftover=session['leftover'])

@app.route('/utilities', methods=['POST'])
def utilities():
    if request.method == 'POST':
        session['food'] = request.form['food']
        session['leftover'] = float(session['leftover']) - float(session['food'])
        return render_template('utilities.html',
                               leftover=session['leftover'])

@app.route('/insurance', methods=['POST'])
def insurance():
    if request.method == 'POST':
        session['bills'] = float(request.form['gas_bill']) + float(request.form['electric_bill']) + float(request.form['internet_bill']) + float(request.form['city_bill'])
        session['leftover'] = float(session['leftover']) - float(session['bills'])
        return render_template('insurance.html', leftover=session['leftover'])

@app.route('/entertainment', methods=['POST'])
def fun():
    if request.method == 'POST':
        session['leftover'] = float(session['leftover']) - float(request.form['insurance']) -float(request.form['life'])
        return render_template('entertainment.html', leftover=session['leftover'])

@app.route('/services', methods=['POST'])
def services():
    if request.method == 'POST':
        session['leftover'] = float(session['leftover']) - float(request.form['derek']) - float(request.form['taylor']) - float(request.form['outings']) - float(request.form['dates'])
        return render_template('services.html', leftover=session['leftover'])

@app.route('/health', methods=['POST'])
def health():
    if request.method == 'POST':
        session['services'] = float(request.form['hulu']) + float(request.form['spotify']) + float(request.form['amc']) + float(request.form['amazon'])
        session['leftover'] = session['leftover'] - session['services']
        return render_template('health.html',
                               leftover=session['leftover'])

@app.route('/savings', methods=['POST'])
def savings():
    if request.method == 'POST':
        session['health'] = float(request.form['health'])
        session['leftover'] = session['leftover'] - session['health']
        return render_template('savings.html',
                               leftover=session['leftover'])

@app.route('/results', methods=['POST'])
def results():
    if request.method == 'POST':
        housing = request.form['housing']
        session['savings_and_givings'] = float(request.form['savings']) - float(request.form['giving'])
        session['leftover'] = session['leftover'] - session['savings_and_givings']
        today = date.today()
        return render_template('results.html',
                               leftover=session['leftover'],
                               date=today,)


app.run(debug = True)

错误回溯：

Traceback (most recent call last):
File "/python3.7/site-packages/flask/app.py", line 2463, in __call__
return self.wsgi_app(environ, start_response)
File "/python3.7/site-packages/flask/app.py", line 2449, in wsgi_app
response = self.handle_exception(e)
File "/python3.7/site-packages/flask/app.py", line 1866, in handle_exception
reraise(exc_type, exc_value, tb)
File "/python3.7/site-packages/flask/_compat.py", line 39, in reraise
raise value
File "/python3.7/site-packages/flask/app.py", line 2446, in wsgi_app
response = self.full_dispatch_request()
File "/python3.7/site-packages/flask/app.py", line 1951, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/python3.7/site-packages/flask/app.py", line 1820, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/python3.7/site-packages/flask/_compat.py", line 39, in reraise
raise value
File "/python3.7/site-packages/flask/app.py", line 1949, in full_dispatch_request
rv = self.dispatch_request()
File "/python3.7/site-packages/flask/app.py", line 1935, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "budget/budget.py", line 84, in results
housing = request.form['housing']
File "/python3.7/site-packages/werkzeug/datastructures.py", line 443, in __getitem__
raise exceptions.BadRequestKeyError(key)
werkzeug.exceptions.BadRequestKeyError: 400 Bad Request: The browser(or proxy) sent a request that this server could not understand.
KeyError: 'housing'

关于为什么会发生这种情况的任何想法？ 提前致谢

Answer 1

试图从表单中不存在的表单中获取值。 这里housing = request.form['housing']

当使用session['housing'] = request.form["housing"]将数据存储在flask session 中时，数据将存储在用户的浏览器 Z55E7DD3016CE4AC57B9A0F56AF12F 中，并在用户重新启动浏览器时清除。

@app.route('/results', methods=['POST'])
def results():
    if request.method == 'POST':
        housing = session['housing']
        session['savings_and_givings'] = float(request.form['savings']) - float(request.form['giving'])
        session['leftover'] = session['leftover'] - session['savings_and_givings']
        today = date.today()
        return render_template('results.html',
                               leftover=session['leftover'],
                               date=today,)

如果值不存在，使用get提供默认值

session['income'] = request.form.get("income", 0)

使用session.clear()清除用户 cookies 中的所有数据

@app.route('/', methods=['GET'])
def entry():
        session.clear()
        return render_template('entry.html',
                           the_title='Smith Family Budgeting')

Answer 2

Web 页面是无状态的，您只是无法保存它们的 state。 如果您稍后需要获取操作结果，请考虑将数据保存到某个文件或使用任何 SQL 数据库。 对于小型项目和培训，我推荐 SQLITE3，它已经是 Python 标准库的一部分，并与您的其他项目文件（.py、.htmls、.css 等）一起存储为多个文件（模式 + db 本身）

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