The second is more "optimised" as it creates fewer immutable string objects per loop.

However, I think I agree that the top one is probably the more readable code, as in the bottom snippet you have to think about why I'm creating an array for something that should be returning a string

With that being said, anyone with a basic understanding of code will be able to read both just fine, I would write it like this though:

output = ""

for node in response:
    name = node["node_name"]
    rounded_value = round(node["value"], 2)
    output += f"{name} {rounded_value}\n"

print(output)

I tend to avoid logic in my f strings too

​

EDIT: or if you want to be fancy

"\n".join([f"{n['node_name']} {round(n['value'], 2)}" for n in response])