python,django,database,table,many-to-many , django - Many To Many relationship issue


django - Many To Many relationship issue

Question:

Tag: python,django,database,table,many-to-many

I am working in django, am planning a database for rides for users.

each Ride can have multiple Users (passengers) on it, and multiple middle-destinations in it. also, each Destination can be in multiple Rides and each User (passenger) can be on multiple Rides (overtime).

Also, for each Ride there will be only one final destination and only one driver (also a User).

This is my code:

def get_image_path(models.Model):
    return os.path.join('photos',str(instance.id),filename)


class UserProfile(models.Model):
    user=models.OneToOneField(User)
    phone_number=models.CharField(max_length=12)
    profile_picture=models.ImageField(upload_to=get_image_path, black=True, null=True)

class Ride(models.Model):
    driver=models.ForeignKey(UserProfile, related_name="r_driver")
    destination=models.ForeignKey(Destination, related_name="r_final_destination")
    leaving_time=models.DateTimeField()
    num_of_spots=models.IntergerField()
    passengers=models.ManyToMany(UserProfile, related_name="r_passengers")
    mid_destinations=models.ManyToMany(Destination, related_name="r_mid_destinations")

class Destination(models.Model):
    name=models.CharField(max_length=30)

The Issue is - when a User adds a Ride, I want the driver, destination and mid_destinations and the rest of the fields to be set by the User (the driver is the User adding the Ride), Except for the passengers field. I want the other Users to add themselves to the ride, so when the Ride is created the User (driver) doesn't have to set the passengers.

How do I go about it? and also, any other suggestions about the models?

thanks a lot!


Answer:

About the first part of the question

The Issue is - when a User adds a Ride, I want the driver, destination and mid_destinations and the rest of the fields to be set by the User (the driver is the User adding the Ride), Except for the passengers field.

The django.forms way

You just need a custom Form and handle manually the driver field. Something like this:

class DriverRideForm(forms.ModelForm):
    class Meta:
        model = Ride
        exclude = ('driver', 'passengers', )

And then in the view where request.user is the driver

form = DriverRideForm(request.POST)
if form.is_valid():
    ride = form.save(commit=False)
    ride.driver = request.user.userprofile
    ride.save()

The django-rest-framework way

You can but you will probably do not want to exclude the driver from the serializer fields. This is because usually only one serializer is used per ViewSet so you will want to return that field to the consumer of the API.

So you have two options:

How a user can add himself with read-only passengers field?

I would probably do it with a custom endpoint (with @detail_route). Something like this:

class RideViewSet(...):

    #...

    @detail_route(methods=['post'])
    def attach(self, request, pk=None):
        ride = self.get_object()
        ride.passengers.add(request.user.userprofile)
        return Response(self.get_serializer(ride).data)

This way just POST-ing at url like /api/rides/<id>/attach/ will add the logged in request.user to the ride.passengers.

About the second part of the question

any other suggestions about the models?

I think your model structure is fine. I can only think of that in the future you may need more meta data about the relations, so it may be a good moment to be prepared with some Intermediate Models, something like:

class Ride(models.Model):
    # ...
    passengers=models.ManyToMany(UserProfile, through='RideSeat', related_name="r_passengers")
    mid_destinations=models.ManyToMany(Destination, through='RideMidDestination', related_name="r_mid_destinations")


class RideSeat(models.Model):
    ride = models.ForeignKey(Ride)
    passenger = models.ForeignKey(UserProfile)
    seat_number = models.IntegerField()


class RideMidDestination(models.Model):
    ride = models.ForeignKey(Ride)
    destination = models.ForeignKey(Destination)
    arrival_time = models.DateTimeField()

Related:


Identify that a string could be a datetime object


python,regex,algorithm,python-2.7,datetime
If I knew the format in which a string represents date-time information, then I can easily use datetime.datetime.strptime(s, fmt). However, without knowing the format of the string beforehand, would it be possible to determine whether a given string contains something that could be parsed as a datetime object with the...

Django: html without CSS and the right text


python,html,css,django,url
First of all, this website that I'm trying to build is my first, so take it easy. Thanks. Anyway, I have my home page, home.html, that extends from base.html, and joke.html, that also extends base.html. The home page works just fine, but not the joke page. Here are some parts...

How do variables inside python modules work?


python,module,python-module
I am coming from a Java background with Static variables, and I am trying to create a list of commonly used strings in my python application. I understand there are no static variables in python so I have written a module as follows: import os APP_NAME = 'Window Logger' APP_DATA_FOLDER_PATH...

Sort when values are None or empty strings python


python,list,sorting,null
I have a list with dictionaries in which I sort them on different values. I'm doing it with these lines of code: def orderBy(self, col, dir, objlist): if dir == 'asc': sorted_objects = sorted(objlist, key=lambda k: k[col]) else: sorted_objects = sorted(objlist, key=lambda k: k[col], reverse=True) return sorted_objects Now the problem...

Pandas - Dropping multiple empty columns


python,pandas
I have some tables where the first 11 columns are populated with data, but all columns after this are blank. I tried: df=df.dropna(axis=1,how='all') which didn't work. I then used: df = df.drop(df.columns[range(11,36)], axis=1) Which worked on the first few tables, but then some of the tables were longer or shorter...

Pandas Dataframe Complex Calculation


python,python-2.7,pandas,dataframes
I have the following dataframe,df: Year totalPubs ActualCitations 0 1994 71 191.002034 1 1995 77 2763.911781 2 1996 69 2022.374474 3 1997 78 3393.094951 I want to write code that would do the following: Citations of currentyear / Sum of totalPubs of the two previous years I want something to...

Create an exe with Python 3.4 using cx_Freeze


python,python-3.4,cx-freeze
I have found two other articles about this problem on Stack Exchange but none of them has a clear answer: is it possible to create a .exe of a Python 3.4 script? The only solution I found was to use cx_Freeze. I used it, and it indeed created an executable...

trying to understand LSH through the sample python code


python,similarity,locality-sensitive-hash
the concise python code i study for is here Question A @ line 8 i do not really understand the syntax meaning for "res = res << 1" for the purpose of "get_signature" Question B @ line 49 (SOLVED BY myself through another Q&A) "xor = r1^r2" does not really...

SyntaxError: invalid syntax?


python,syntax
Good afternoon, I am developing a script in python and while I am trying to compile it from the terminator/terminal i always get this error, but I cannot understand where is the syntax error? File "_case1.py", line 128 print ('########################') ^ SyntaxError: invalid syntax Then I just change the position...

Matplotlib: Plot the result of an SQL query


python,sql,matplotlib,plot
from sqlalchemy import create_engine import _mssql from matplotlib import pyplot as plt engine = create_engine('mssql+pymssql://**:****@127.0.0.1:1433/AffectV_Test') connection = engine.connect() result = connection.execute('SELECT Campaign_id, SUM(Count) AS Total_Count FROM Impressions GROUP BY Campaign_id') for row in result: print row connection.close() The above code generates an array: (54ca686d0189607081dbda85', 4174469) (551c21150189601fb08b6b64', 182) (552391ee0189601fb08b6b73', 237304) (5469f3ec0189606b1b25bcc0',...

Sum of two variables in RobotFramework


python,automated-tests,robotframework
I have two variables: ${calculatedTotalPrice} = 42,42 ${productPrice1} = 43,15 I executed ${calculatedTotalPrice} Evaluate ${calculatedTotalPrice}+${productPrice1} I got 42,85,15 How can I resolve it?...

How can I resolve my variable's unexpected output?


django,python-2.7
I have a variable in django named optional_message. If I debug the variable then it says Swenskt but when I try to print the variable on my page the following comes out: (u'Swenskt',) and the variable can't be tested for its length etc. What should I do if I only...

The event loop is already running


python,python-3.x,pyqt,pyqt4
I have the following 5 files: gui.py # -*- coding: utf-8 -*- from PyQt4 import QtCore, QtGui try: _fromUtf8 = QtCore.QString.fromUtf8 except AttributeError: def _fromUtf8(s): return s try: _encoding = QtGui.QApplication.UnicodeUTF8 def _translate(context, text, disambig): return QtGui.QApplication.translate(context, text, disambig, _encoding) except AttributeError: def _translate(context, text, disambig): return QtGui.QApplication.translate(context, text, disambig)...

Spring-integration scripting with Python


python,spring-integration,jython
I'm trying to use Python with spring-integration and jython-standalone-2.7.0: Here is my application context: <int:inbound-channel-adapter id="in" channel="exampleChannel" > <int:poller fixed-rate="1000" /> <int-script:script lang="python" location="script/message.py" /> </int:inbound-channel-adapter> <int:channel id="exampleChannel" /> <int-ip:udp-outbound-channel-adapter id="udpOut" channel="exampleChannel" host="192.168.0.1" port="11111" /> Here is my script in Python: print "Python"...

Python: can't access newly defined environment variables


python,bash,environment-variables
I can't access my env var: import subprocess, os print os.environ.get('PATH') # Works well print os.environ.get('BONSAI') # doesn't work But the env var is well added in my /home/me/.bashrc: BONSAI=/home/me/Utils/bonsai_v3.2 export BONSAI And I can access this env var from a new terminal....

Find the tf-idf score of specific words in documents using sklearn


python,scikit-learn,tf-idf
I have code that runs basic TF-IDF vectorizer on a collection of documents, returning a sparse matrix of D X F where D is the number of documents and F is the number of terms. No problem. But how do I find the TF-IDF score of a specific term in...

How to use template within Django template?


python,html,django,templates,django-1.4
I have the django template like below: <a href="https://example.com/url{{ mylist.0.id }}" target="_blank"><h1 class="title">{{ mylist.0.title }}</h1></a> <p> {{ mylist.0.text|truncatewords:50 }}<br> ... (the actual template is quite big) It should be used 10 times on the same page, but 'external' html elements are different: <div class="row"> <div class="col-md-12 col-lg-12 block block-color-1"> *django...

Using .update with nested Serializer to post Image


django,rest,django-models,django-rest-framework,imagefield
I have an ImageField. When I update it with the .update command, it does not properly save. It validates, returns a successful save, and says it is good. However, the image is never saved (I don't see it in my /media like I do my other pictures), and when it...

How to remove structure with python from this case?
python,python-2.7
How to remove "table" from HTML using python? I had case like this: paragraph = ''' <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Quidem molestiae consequuntur officiis corporis sint.<br /><br /> <table> <tr> <td> text title </td> <td> text title 2 </td> </tr> </table> <p> lorem ipsum</p> ''' how...

How do I read this list and parse it?


python,list
I'm using requests and the output I get from the sites API is a list, I've been stuck trying to parse it to get the data from it. I use r = requests.get(urlas, params=params) r.json() to get the data I want. Here is a snippet of the list [{'relation_type': None,...

Django block inclusion not working. What did I miss?


django,django-templates
In my base.html file I have this: {% block menu %}{% endblock menu %} and in base_menu.html I have this: {% extends "base.html" %} {% block menu %} <nav class="navbar navbar-inverse navbar-fixed-top"> ... stuff ... </div> {% endblock menu %} I would expect the menu html to show where the...

Strange Behavior: Floating Point Error after Appending to List


python,python-2.7,behavior
I am writing a simple function to step through a range with floating step size. To keep the output neat, I wrote a function, correct, that corrects the floating point error that is common after an arithmetic operation. That is to say: correct(0.3999999999) outputs 0.4, correct(0.1000000001) outputs 0.1, etc. Here's...

Create angular page in Django to consume data from JSON


angularjs,django,django-templates
In an angular controller I have a list of items: app.controller('MainController', ['$scope', function($scope) { $scope.items = [ {"foo":"bar 1"}, {"foo":"bar 2"}, {"foo":"bar n"} ] }]); The following html page, based on angular, displays a list of item: <!DOCTYPE html> <html> <head> <title>list</title> <script src= "http://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js"></script> </head> <body data-ng-app="myApp"> <div data-ng-controller="MainController">...

odoo v8 - Field(s) `arch` failed against a constraint: Invalid view definition


python,xml,view,odoo,add-on
I want to create a new view with a DB-view. When I try to install my app, DB-view was created then I get error: 2015-06-22 12:59:10,574 11988 ERROR odoo openerp.addons.base.ir.ir_ui_view: Das Feld `datum` existiert nicht Fehler Kontext: Ansicht `overview.tree.view` [view_id: 1532, xml_id: k. A., model: net.time.overview, parent_id: k. A.] 2015-06-22...

Inserting a variable in MongoDB specifying _id field


python,mongodb,pymongo
I want to insert a variable, say, a = {1:2,3:4} into my database with a particular id "56". It is very clear from the docs that I can do the following: db.testcol.insert({"_id": "56", 1:2, 3:4}) However, I cannot figure out any way to insert "a" itself, specifying an id. In...

Callable in model field not called upon adding new object through Django admin


django,django-models,django-admin
In https://docs.djangoproject.com/en/1.8/ref/models/fields/#django.db.models.Field.default we read that the callable of a default field value is called, every time a new object is created. In my model I have: when_first_upload = models.DateTimeField(default=datetime.datetime.now()) When in the admin page I create a new object I always get the same datetime, as if the callable is...

Twilio Client Python not Working in IOS Browser


javascript,python,ios,flask,twilio
I have created a simple twilio client application to make phone calls from Web Browser to phones. I used a sample Flask app to generate a secure Capability Token and used twilio.min.js library to handle calls from my HTML. The functionality works fine in Computer Browsers ans Android Phone Browsers,...

Python: histogram/ binning data from 2 arrays.


python,histogram,large-files
I have two arrays of data: one is a radius values and the other is a corresponding intensity reading at that intensity: e.g. a small section of the data. First column is radius and the second is the intensities. 29.77036614 0.04464427 29.70281027 0.07771409 29.63523525 0.09424901 29.3639355 1.322793 29.29596385 2.321502 29.22783249...

Python - Opening and changing large text files


python,replace,out-of-memory,large-files
I have a ~600MB Roblox type .mesh file, which reads like a text file in any text editor. I have the following code below: mesh = open("file.mesh", "r").read() mesh = mesh.replace("[", "{").replace("]", "}").replace("}{", "},{") mesh = "{"+mesh+"}" f = open("p2t.txt", "w") f.write(mesh) It returns: Traceback (most recent call last): File...

How to change the IP address of Amazon EC2 instance using boto library


python,amazon-web-services,boto
How can I assign a new IP address (or Elastic IP) to an already existing AWS EC2 instance using boto library.

Peewee: reducing where conditionals break after a certain length


python,peewee
This is what I have: SomeTable.select.where(reduce(operator.or_, (SomeTable.stuff == entry for entry in big_list))) The problem arises when I have a relatively large list of elements in big_list and I get this: RuntimeError: maximum recursion depth exceeded Is there another way to approach this that doesn't involve splitting up the list...

How does the class_weight parameter in scikit-learn work?


python,scikit-learn
I am having a lot of trouble understanding how the class_weight parameter in scikit-learn's Logistic Regression operates. The Situation I want to use logistic regression to do binary classification on a very unbalanced data set. The classes are labelled 0 (negative) and 1 (positive) and the observed data is in...

group indices of list in list of lists


python,list
I am looking for an elegant solution for the following problem. I have a list of ints and I want to create a list of lists where the indices with the same value are grouped together in the order of the occurrences of said list. [2, 0, 1, 1, 3,...

Python recursive function not recursing


python,recursion
I'm trying to solve a puzzle, which is to reverse engineer this code, to get a list of possible passwords, and from those there should be one that 'stands out', and should work function checkPass(password) { var total = 0; var charlist = "abcdefghijklmnopqrstuvwxyz"; for (var i = 0; i...

SQLAlchemy. 2 different relationships for 1 column


python,sqlalchemy
I have a simple many-to-many relationship with associated table: with following data: matches: users: users_mathces: ONE user can play MANY matches and ONE match can involve up to TWO users I want to realize proper relationships in both "Match" and "User" classes users_matches_table = Table('users_matches', Base.metadata, Column('match_id', Integer, ForeignKey('matches.id', onupdate="CASCADE",...

Replace nodejs for python?


python,node.js,webserver
i'm working in a HTML5 multiplayer game, and i need a server to sync player's movement, chat, battles, etc. So I'm looking for ways to use python instead nodejs, because i have I have more familiarity with python. The server is simple: var express = require('express'); var app = express();...

sys.argv in a windows environment


python,windows,python-3.x
I'm attempting to learn python using the book 'a byte of python'. The code: import sys print('the command line arguments are:') for i in sys.argv: print(i) print('\n\nThe PYTHONPATH is', sys.path, '\n') outputs: the command line arguments are: C:/Users/user/PycharmProjects/helloWorld/module_using_sys.py The PYTHONPATH is ['C:\\Users\\user\\PycharmProjects\\helloWorld', 'C:\\Users\\user\\PycharmProjects\\helloWorld', 'C:\\Python34\\python34.zip', 'C:\\Python34\\DLLs', 'C:\\Python34\\lib', 'C:\\Python34', 'C:\\Python34\\lib\\site-packages']...

Using counter on array for one value while keeping index of other values


python,collections
After reading the answers on this question How to count the frequency of the elements in a list? I was wondering how to count the frequency of something, and at the same time retreive some extra information, through something like an index. For example a = ['fruit','Item#001'] b = ['fruit','Item#002']...

How to check for multiple attributes in a list


python,python-2.7
I am making a TBRPG game using Python 2.7, and i'm currently making a quest system. I wanted to make a function that checks all of the quests in a list, in this case (quests), and tells you if any of of the quests in the list have the same...

represent an index inside a list as x,y in python


python,list,numpy,multidimensional-array
I have a list which contains 1000 integers. The 1000 integers represent 20X50 elements of dimensional array which I read from a file into the list. I need to walk through the list with an indicator in order to find close elements to each other. I want that my indicator...

Python Popen - wait vs communicate vs CalledProcessError


python,python-2.7,error-handling,popen
Continuing from my previous question I see that to get the error code of a process I spawned via Popen in python I have to call either wait() or communicate() (which can be used to access the Popen stdout and stderr attributes): app7z = '/path/to/7z.exe' command = [app7z, 'a', dstFile.temp,...

Calling function and passing arguments multiple times


python,function,loops
I want to call the function multiple time and use it's returned argument everytime when it's called. For example: def myfunction(first, second, third): return (first+1,second+1,third+1) 1st call: myfunction(1,2,3) 2nd call is going to be pass returned variables: myfunction(2,3,4) and loop it until defined times. How can I do such loop?...

how to enable a entry by clicking a button in Tkinter?


python,tkinter
I need to activate many entries when button is clicked please do not write class based code, modify this code only because i need to change the whole code for the project as i did my whole project without classes from Tkinter import * import ttk x='disabled' def rakhi(): global...

Displaying a 32-bit image with NaN values (ImageJ)


python,image-processing,imagej
I wrote a multilanguage 3-D image denoising ImageJ plugin that does some operations on an image and returns the denoised image as a 1-D array. The 1-D array contains NaN values (around the edges). The 1-D array is converted back into an image stack and displayed. It is simply black....

Count function counting only last line of my list


python,python-2.7
Count function counting only last line of my list N = int(raw_input()) cnt = [] for i in range(N): string = raw_input() for j in range(1,len(string)): if string[j] =='K': cnt.append('R') elif string[j] =='R': cnt.append('R') if string[0] == 'k': cnt.append('k') elif string[0] == 'R': cnt.append('R') print cnt.count('R') if I am giving...

How to put an image on another image in python, using ImageTk?


python,user-interface,tkinter
I want to put an image in front of another one, then use this combined image as a button's background image in Tkinter. How can I do it? I am free to import Tkimage, Image. Clarify: I want to stick this on the center of this so that something like...

In sklearn, does a fitted pipeline reapply every transform?


python,scikit-learn,pipeline,feature-selection
Apologies if this is obvious but I couldn't find a clear answer to this: Say I've used a pretty typical pipeline: feat_sel = RandomizedLogisticRegression() clf = RandomForestClassifier() pl = Pipeline([ ('preprocessing', preprocessing.StandardScaler()), ('feature_selection', feat_sel), ('classification', clf)]) pl.fit(X,y) Now when I apply pl on a new set, pl.predict(X_classify); is RandomizedLogisticRegression going...

Parse text from a .txt file using csv module


python,python-2.7,parsing,csv
I have an email that comes in everyday and the format of the email is always the same except some of the data is different. I wrote a VBA Macro that exports the email to a text file. Now that it is a text file I want to parse the...