Python: How to create new variables in for loops?

Question

I'm trying to create several arrays in a loop and have access to them further on. I don't understand why I can modify and print them within the loop but outside it says the variable doesn't exist.

for i in range (0,3):
    a_i=[i]
    a_i.append(i+1)
    print a_i
print a_1

Is there anyone who can give me a suggestion on how to fix the problem?

Have a read through en.wikipedia.org/wiki/Scope_(computer_science) — jbowes
– jbowes, Commented Nov 18, 2012 at 15:14
There's no reason to downvote someone because their code is wrong. Their code being wrong is why they're asking the question. — Zero Piraeus
– Zero Piraeus, Commented Nov 18, 2012 at 15:17
@flabons Welcome to StackOverflow! Let me inform you that is not a forum, it's a Q&A site. If you want to discuss an answer, use "add comment". If you want to provide additional details, edit your question, we'll notice. Only use "Answer" when you're providing a solution to a question. — Kos
– Kos, Commented Nov 18, 2012 at 15:35

Kos · Accepted Answer · 2012-11-18 15:16:50Z

8

Variables name are tokens used as-is, i.e. variables aren't expanded inside other variable names.

You can't expect a_i to be equal to a_1 if i == 1.

For that, use arrays or dictionaries.

a = {}
for i in range (0,3):
    a[i] = [i]
    a[i].append(i+1)
    print a[i]
print a
print a[1]

answered Nov 18, 2012 at 15:16

Kos

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