Mixing
Flask return redirect(url_for) error for missing parameter
Clash Royale CLAN TAG#URR8PPP Flask return redirect(url_for) error for missing parameter
I have the following code and when I try a return redirect(url_for) on the present and future functions I get the following error message:
return redirect(url_for)
present
future
TypeError: home() missing 1 required positional argument: 'calc_type'
I've tried multiple ways to pass the calc_type variable to the home function and always get the same error. Any help is appreciated.
calc_type
home
from flask import render_template, redirect, url_for, request
from app import app, db
from models import Pres, Future
@app.route('/home')
def home(calc_type):
if (calc_type == "present"):
try:
inputs = Pres.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
pv = cash / (1 + rate)**periods
return render_template('present.html', inputs=inputs, cash=cash, pv=pv)
except:
return render_template('present.html')
elif (calc_type == "future"):
inputs = Future.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
fv = cash * (1 + rate)**periods
return render_template('present.html', inputs=inputs, cash=cash, fv=fv)
@app.route('/present', methods=['GET', 'POST'])
def present():
input = Pres(request.form['cash'], request.form['rate'], request.form['periods'])
calc_type = "present"
db.session.add(input)
db.session.commit()
return redirect(url_for('home', calc_type=calc_type))
@app.route('/future', methods=['GET', 'POST'])
def future():
input = Future(request.form['cash'], request.form['rate'], request.form['periods'])
calc_type = "future"
db.session.add(input)
db.session.commit()
return redirect(url_for('home', calc_type=calc_type))
calc_value
/home
ur_for()
I expect it to be a string of either "present" or "future" that will then be used in the "if (calc_type = "present)" condition in the 'home' function. My html has a dropdown where the user can select either a present value or a future value calculation. That's all working fine. I just can't get the parameter to pass. Or the 'home' function to accept it.
– jpanknin
13 hours ago
1 Answer
1
The way you have your home() view, there is no way for it to receive a parameter from url_to because there is no such a variable in the route's path.
home()
url_to
View functions are wrapped by flask and will behave differently than regular functions.
For the home view to receive the variable you would have to define it with a variable in it's route path:
@app.route('/home/<string:calc_type>')
def home(calc_type):
...
# Result:
>>> url_for('route', calc_type='present')
'/home/present'
Alternatively, you can pass it as url query variables:
@app.route('/home')
def home():
calc_type = request.args.get('calc_type')
# Result:
>>> url_for('route', calc_type='present')
'/home?calc_type=present'
But most importantly, you should also try to separate view/routing logic from other code and keep your views as light as possible.
Here are two ways you could solve this:
Option 1
PS: I would not do it this way, but is the closest to your code as is.
def get_view(calc_type):
if (calc_type == "present"):
try:
inputs = Pres.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
pv = cash / (1 + rate)**periods
return render_template('present.html', inputs=inputs, cash=cash, pv=pv)
except:
return render_template('present.html')
elif (calc_type == "future"):
inputs = Future.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
fv = cash * (1 + rate)**periods
return render_template('present.html', inputs=inputs, cash=cash, fv=fv)
@app.route('/present', methods=['GET', 'POST'])
def present():
input = Pres(request.form['cash'], request.form['rate'], request.form['periods'])
calc_type = "present"
db.session.add(input)
db.session.commit()
return get_view(calc_type)
@app.route('/future', methods=['GET', 'POST'])
def future():
input = Future(request.form['cash'], request.form['rate'], request.form['periods'])
calc_type = "future"
db.session.add(input)
db.session.commit()
return get_view(calc_type)
Option 2
# calculations.py
from models import Pres, Future
def present_calc():
try:
inputs = Pres.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
pv = cash / (1 + rate)**periods
return dict(inputs=inputs, cash=cash, pv=pv)
except:
return dict()
def future_calc():
inputs = Future.query.all()
for item in inputs:
cash = item.cash
rate = item.rate
periods = item.periods
fv = cash * (1 + rate)**periods
return dict(inputs=inputs, cash=cash, fv=fv)
# views.py
from flask import render_template, redirect, url_for, request
from app import app, db
from .calculations import present_calc, future_calc
from app import db
@app.route('/present', methods=['GET', 'POST'])
def present():
inputs = Pres(
cash=request.form['cash'],
rate=request.form['rate'],
periods=request.form['rate'])
db.session.add(inputs)
db.session.commit()
calcs = present_calc()
return render_template('present.html', **calcs)
@app.route('/future', methods=['GET', 'POST'])
def future():
inputs = Pres(
cash=request.form['cash'],
rate=request.form['rate'],
periods=request.form['rate'])
db.session.add(inputs)
db.session.commit()
calcs = future_calc()
return render_template('future.html', **calcs)
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What are you expecting
calc_valueto be when you access/home? It should probably be either be a query param, or be part of or url You can pass a value usingur_for()when the value is part of the url: @app.route('/home/<string:calc_type>'): def home(calc_type):– gtalarico
13 hours ago