Create an instance of a random class

Question

i'm currently making a text-based game on python and i have a question. I have classes for some rooms like RoomSpider, RoomSoldier, RoomDragon, etc. and I want to create a map (3d array) and fill some rooms with an instance of a random class.

For example:

[[RoomSpider, RoomSoldier],
[RoomSoldier,RoomDragon]]

How can I do to create an instance of a random class?

Looking for this http://stackoverflow.com/questions/4821104/python-dynamic-instantiation-from-string-name-of-a-class-in-dynamically-imported ? — fghj, Oct 28 '15 at 00:53

score 4 · Accepted Answer · answered Oct 28 '15 at 01:05

4

To make an instance of a random class:

import random
classes = (RoomSpider, RoomSoldier, RoomDragon, 
           RoomElephant, RoomPixie)

# choose a random class from the list and instantiate it
instance = random.choice(classes)()

answered Oct 28 '15 at 01:05

donkopotamus

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How about classes with arguments? What if it randomly chose one class which has more arguments than the others? – Alteros Sep 01 '20 at 02:11
@Alteros Using this approach then either all your classes need to expose a common constructor api (using `*args` or `**kw` if required), or you'll need factory functions with a common api – donkopotamus Sep 01 '20 at 05:02

score 1 · Answer 2 · answered Oct 28 '15 at 01:05

1

Take a look at random.choice, it lets you choose a random element from a sequence.

from random import choice
classes = (RoomSpider, RoomSoldier, RoomDragon, ...)
room = [[choice(classes)() for _ in range(2)] for __ in range(2)]

answered Oct 28 '15 at 01:05

L3viathan

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score 1 · Answer 3 · answered Oct 28 '15 at 01:07

Classes are first-class objects in Python, which means that you can store them in variables and pass them around. So for instance, you could make a list/tuple of all your possible classes and then pick random ones:

import random

room_classes = (RoomSpider, RoomSoldier, RoomDragon)
room_map = []

for row in range(5):
    room_row = []
    for col in range(5):
        room_class = random.choice(room_classes) # picks a random class
        room_row.append(room_class())            # creates an instance of that class
    room_map.append(room_row)

This uses random.choice() to generate a 5x5 set of randomly chosen instances.

Create an instance of a random class

3 Answers3