Python : Call list attribute from a list of defined attributes

Question

I have a list with list operations, For example ["insert", "append"], For now I am doing like if list says insert then I am calling .insert.

Check below code

In [31]: list_ops = [ "insert" , "append" ]

In [32]: list1 = [ 1 , 3 , 5 ]

In [33]: if list_ops[0] == "insert" :
    ...:     list1.insert(3, 7)
    ...:

In [34]: list1
Out[34]: [1, 3, 5, 7]

In [35]: list1.list_ops[0](4, 9 )
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-35-5db0dcceeac1> in <module>
----> 1 list1.list_ops[0](4, 9 )

AttributeError: 'list' object has no attribute 'list_ops'

In [36]:

How can I choose the operation from list_ops itself instead of doing if-else matching.

Thank you.

im pretty sure you cant.

notacorn
– notacorn

2020-05-29 05:32:40 +00:00
Commented May 29, 2020 at 5:32 — notacorn
– notacorn, Commented May 29, 2020 at 5:32

Prune · Accepted Answer · 2020-05-29 05:36:57Z

2

You can't choose an operation from list_ops, because it's a list of strings, not of operations. You need to choose the operation based on the string. For instance:

list_ops = {
    "insert": list.insert,
    "append": list.append
}

Now you can choose the operation based on the input string. Can you take it from here?

edited May 29, 2020 at 5:36

answered May 29, 2020 at 5:33

Prune

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Comments

heittpr · Accepted Answer · 2020-05-29 05:46:36Z

0

You could use exec and f-Strings if you really wanted to do it:

operation = "append"
list1 = [1, 2, 3]

exec(f"list1.{operation}(4)")
print(list1) # [1, 2, 3, 4]

But to be honest, I think it's a better idea to create an operation dictionary like Prune suggested.

answered May 29, 2020 at 5:46

heittpr

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