How to create an instance of a class from a string name of the instance?

Question

I would like to create several instances of a Class, I tried to make a for loop to name them differently. Something like this, which doesn't work because the instance name is not supposed to be a string:

class A:
    pass

for i in range(10):
    "a"+str(i) = A()

Here the result I expect is 10 instances of the class A named: a0, a1, ... , a9.

How should I do?

@Carcigenicate That's right, never thank about this. Thank you — Clément Darne, Mar 31 '20 at 17:31

score 2 · Accepted Answer · answered Mar 31 '20 at 17:24

2

You can use dictionaries,

classes = {}
for i in range(10):
    classes[f"a{i}"]  = A()

Then you can access the class instance like this classes["a7"].

answered Mar 31 '20 at 17:24

Shubham Sharma

68,127
6
24
53

I like the idea, I didn't know it was possible this way. Thank you. – Clément Darne Mar 31 '20 at 17:44

score 0 · Answer 2 · answered Mar 31 '20 at 17:24

0

i can think in two ways. The trash way and a good way

Thrash:

class A:
    pass

for i in range(10):
    eval("a"+str(i)) = A()

Good:

class A:
    pass

a= []
for i in range(10):
    a[i] = A()

answered Mar 31 '20 at 17:24

Jasar Orion

626
7
26

I tried the first, **eval()** doesn't work. For the second it's a good idea, I replaced **a[i]** with **a.append()** and it worked. Thank you – Clément Darne Mar 31 '20 at 17:41
eval only work for testing purposes i runned here and it worked. but append is a better ideia and works like a[i] – Jasar Orion Mar 31 '20 at 17:45
Ok, I don't know that much about eval(), but for the list I got an index out of range error, that's why I changed it to append – Clément Darne Mar 31 '20 at 17:48
its becouse you must to start from 0 and when you use range you start from 1 – Jasar Orion Mar 31 '20 at 17:49
Is it not because when created, the list has no "slot" available? I mean it's length is equal to 0. – Clément Darne Mar 31 '20 at 18:02
ok, its nice to know – Jasar Orion Mar 31 '20 at 18:03

How to create an instance of a class from a string name of the instance?

2 Answers2