How can I create a class instance from a list Python

Question

I'm making a program for a school project. It's a Model United Nations.

countries = ['Australia', 'Brazil', 'Canada']

class delegate(object):
   def __init__(self, country):
     self.country = country

I have a list with countries and a class called delegate. So, each delegate object must have a country. Normally I would do it like this:

mexico = delegate('Mexico')

And that would be it. But I would like to loop over the country list and create class instances for each. I mean:

australia = delegate('Australia')
brazil = delegate('Brazil')
canada = delegate('Canada')

and so on. How can I make this? Thank you very much!!

I would suggest you re-assess your selection for the answer that helped you. Or at least explain the reasoning why that answer helped you achieve what you are looking for? Currently [this](https://stackoverflow.com/a/44981035/1832539) answer hits exactly what you are looking for. — idjaw, Jul 08 '17 at 00:18
@idjaw Hi, I'm new on Python (also programming) and I tried the answer you indicated and it shows an error, the one I chose did not. I didn't know why, but if you can explain me I'll be glad in changing my chose. Actually, I had. This the error it shows: delegates = {country: Delegate(country) for country in countries} ^ SyntaxError: invalid syntax — Arturo.Mart, Jul 08 '17 at 01:45
I just copy pasted the code and I did not receive a syntax error. I suggest you copy the code and paste it in to a new python file with nothing else and try again to make sure. — idjaw, Jul 08 '17 at 01:47
Specifying the version would have helped people answering the question to provide an answer more relevant to your environment. I currently don't have a 2.6 installed on my end. But that would explain it. — idjaw, Jul 08 '17 at 01:49

Hugh Bothwell · Accepted Answer · 2017-07-08T19:39:07.047

11

Creating named variables from a list is usually a bad idea. Maybe you could try

countries = ['Australia', 'Brazil', 'Canada']

class Delegate(object):    # according to PEP8, class names should be title-case
    def __init__(self, country):
        self.country = country

# create a dict
delegates = {country: Delegate(country) for country in countries}

Edit: as per @SethMMorton, Python 2.6 does not understand dictionary comprehensions (ie what I used above). You can get the same result using

delegates = dict([(country, Delegate(country)) for country in countries])

edited Jul 08 '17 at 19:39

answered Jul 07 '17 at 23:35

Hugh Bothwell

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nit: py3 note for not *needing* to inherit from object explicitly - > `class Delegate:` should suffice. – idjaw Jul 07 '17 at 23:39
I don't understand the dict and when I write it into the program it shows a syntax error. delegates = {country: Delegate(country) for country in countries} ^ SyntaxError: invalid syntax – Arturo.Mart Jul 08 '17 at 00:48
@Arturo.Mart what version of Python are you using? This works perfectly for me in Python 3.5.3. – Hugh Bothwell Jul 08 '17 at 14:07
1

@HughBothwell They are using Python 2.6 (as mentioned in the comments of the question). For that version there are no `dict` comprehensions so you might want to mention that `dict([(country, Delegate(country)) for country in countries])` will work for < Python 2.7. – SethMMorton Jul 08 '17 at 19:22
@HughBothwell I'm using Python 2.6 So if anyone can help me with this I would be very grateful. – Arturo.Mart Jul 08 '17 at 23:55

score 1 · Answer 2 · edited Jul 07 '17 at 23:38

1

[delegate(c) for c in countries]

edited Jul 07 '17 at 23:38

dmitry

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answered Jul 07 '17 at 23:34

saarrrr

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score -3 · Answer 3 · answered Jul 07 '17 at 23:37

-3

I believe you're looking for what's called an anonymous class. This means you're making a class without assigning it to a variable. For example:

country_delegates = []
for country in countries:
    country_delegates.append(delegate(country))

This creates a list of delegate objects, one for each country. If you want to get the delegate belonging to a specific country, you could write a function that searches that list and returns the delegate object for the correct country.

answered Jul 07 '17 at 23:37

KAL

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2

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You aren't making an anonymous class here. You aren't making any class *at all*. I suppose you could torture the `type` constructor to create an "anonymous class", but even then, not really... – juanpa.arrivillaga Jul 07 '17 at 23:49
It's very unfortunate this got accepted which ends up providing very misleading guidance to future readers. – idjaw Jul 08 '17 at 00:17
Could you elaborate? If you have a class called `delegate` this code works fine. I thought an anonymous class was a class instantiated without being assigned to a variable, is that not right? – KAL Jul 09 '17 at 21:19

How can I create a class instance from a list Python

3 Answers3