Initialize class instance in a loop over a list

Question

I have a class where I assign a rating to each instance.

class Team:

def __init__(self, rating):
    "Initialize team with rating"
    self.rating = rating

I would like to be able to loop over a list of ratings, and create an instance for each rating, so if I have a list of ratings and team names, something like this:

scores = [10, 11, 12, 13]
teams = ['tm0', 'tm1', 'tm2', 'tm3']

for t, s in zip(teams, scores):
    t = Team(s)

tm2.rating    # returns 12

The above is not defining an instance of Team like I want it to.

I am new to Python so suspect there is an easy fix, or a more Pythonic way of doing this.

Possible duplicate of How do I create a variable number of variables? — quamrana
– quamrana, Commented Jun 4, 2019 at 16:50

chepner · Accepted Answer · 2019-06-04 16:50:10Z

3

You appear to want a dict that maps each team name to an instance of Team.

scores = [10, 11, 12, 13]
team_names = ['tm0', 'tm1', 'tm2', 'tm3']
teams = {t: Team(s) for t, s in zip(team_names, scores)}

assert teams['tm0'].rating == 10

edited Jun 4, 2019 at 16:50

answered Jun 4, 2019 at 16:40

chepner

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2 Comments

chepner Over a year ago

z2 isn't really necessary, unless you need to save a reference to the object before assigning something else to the key with something like teams['tm2'] = Team(15).

galelamanzi Over a year ago

Sorry, I just deleted the comment you replied to as I thought your edit (which I missed) resolved my question.

PirateNinjas · Accepted Answer · 2019-06-04 16:43:58Z

0

You can achieve what you want here with exec:

for t,s in zip(teams, scores):
    exec(f"{t} = Team({s})")

answered Jun 4, 2019 at 16:43

PirateNinjas

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2 Comments

galelamanzi Over a year ago

Can I ask why this is being downvoted? It works perfectly for me - is it because it is un-Pythonic in some way?

PirateNinjas Over a year ago

Generally speaking I would avoid using exec, as it executes an arbitrary command, which could have unexpected consequences.

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