CODEWITHSUNDEEP
pythonpython-3.x
user762630
user762630

Reputation:

Python how to extend a list as if I was adding these items first time

question = []
question.append({'id' : 5, 'title' : 'First question', 'content' : 'Hi there'})

print("Question", question)

question.append({'username' : 'Ali'})

print("Question", question)

I would like to extend a list as if I was adding these items from stratch. The output of the print statement is:

Question [{'id': 5, 'title': 'First question', 'content': 'Hi there'}, {'username': 'Ali'}]

How should I extend the list so that the print statement outputs this:

Question [{'id': 5, 'title': 'First question', 'content': 'Hi there', 'username': 'Ali'}]

Update: In the real example I tried three approaches. I got these error messages.

question[-1].update({'username' : 'Ali'})

AttributeError: 'dict' object attribute 'update' is read-only

(I've also tried this before)

question["username"] = 'Ali'

TypeError: list indices must be integers or slices, not str

question[0]["username"] = 'Ali'

works fine.

Upvotes: 1

Views: 373

Answers (6)

Anuj
Anuj

Reputation: 1014

What you are doing there is, actually adding a dictionary inside a list.

From what you have asked in the question you would like to add another variable to that dictionary so that it has a username key.

If thats what you want, following is a better way to do it.

question = {} #this will define the dictionary
question['id'] = 5
question['title'] = 'First question'
question['content'] = 'Hi there'

And then add the username value to that dictionary by

question['username'] = 'Ali'

Following line is also equivalent to the first 4 lines of the previous code

question = {'id' : 5, 'title' : 'First question', 'content' : 'Hi there'}

and then add the username key to the dictionary by question['username'] = 'Ali

To answer what you have asked, (which doesnt seem like the right way of doing things)

Now you have a list with single element which is dictionary, so to add values to the dictionary, you need to refer the first element of the list as follows

Instead of using question.append({'username' : 'Ali'}) use question[0]['username'] = 'Ali'

What you did is actually added an element to the list question and hence the output was what you have mentioned.

Upvotes: 0

Harsha Biyani
Harsha Biyani

Reputation: 7268

You can try:

>>> question[0]["username"] = "Ali"
>>> print(question)
[{'username': 'Ali', 'id': 5, 'content': 'Hi there', 'title': 'First question'}]

Upvotes: 0

Ersel Er
Ersel Er

Reputation: 771

Your purpose is adding a new field to your object but you are trying to append a new element {'username' : 'Ali'} to your questions list. So you should first add field 'username': 'Ali' to your object then add this object to your questions list.

Hope this helps:

question = []
your_object = {'id' : 5, 'title' : 'First question', 'content' : 'Hi there'}
your_object['username'] = 'Ali'
question.append(your_object)

print("Question", question)

Upvotes: 0

ymbirtt
ymbirtt

Reputation: 1666

You have a list of dictionaries:

dict_list = [{'foo': 'bar'}]

You're calling dict_list.append, which appends an item to the list

dict_list.append({'baz': 'bork'})
print dict_list # => [{'foo': 'bar'}, {'baz': 'bork'}]

If you want to update the original dictionary, then you should instead retrieve that specific dictionary, and then update that

dict_list = [{'foo': 'bar'}]
dict_list[0]['baz'] = 'bork' # we could also use dict_list[0].update here
print dict_list # => [{'foo': 'bar', 'baz': 'bork'}]

That said, it looks like you're trying to build some kind of structure that holds these questions for easy retrieval. Rather than using a list for this, it might be more sensible to use a dict-of-dicts, where the key of each question was its id, something like:

questions = {}
questions[5] = {'title' : 'First question', 'content' : 'Hi there'}
questions[5]['username'] = 'Ali'

Upvotes: 0

AGN Gazer
AGN Gazer

Reputation: 8378

question = {'id' : 5, 'title' : 'First question', 'content' : 'Hi there'}
# "extend" (=update the dictionary):

question['username'] = 'Ali'

Upvotes: 0

Bhushan Pant
Bhushan Pant

Reputation: 1580

I used this for your query. Not sure if this solves your problem:

question = []
question.append({'id' : 5, 'title' : 'First question', 'content' : 'Hi there'})
question[0]["username"] = "test"
print question

Output: 

[{'content': 'Hi there', 'username': 'test', 'id': 5, 'title': 'First question'}]

Upvotes: 0

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