Python - Use a variable as a list name

Question

I have this code in python.

import sys
list1 = [\"A\", \"B\", \"C\"]
list2 = [1, 2, 3]

myarg = sys.argv[1]
print len(myarg)

I will run thi

Answer 1

You shouldn't, but if you really want/have to do this, you can use globals():

print len(globals()[myarg])

First make sure myarg is the name of a declared variable: if myarg in globals(): ...

Answer 2

Since it is possible, and thought @Lattyware's answer is the correct one, this is how you could do it:

import sys
list1 = ["A", "B", "C"]
list2 = [1, 2, 3]

myarg = sys.argv[1]

print len(globals().get(myarg, []))

If it prints 0, then you have a bad argument on the command line.

Answer 3

While this is entirely possible in Python, it's not needed. The best solution here is to not do this, have a dictionary instead.

import sys

lists = {
    "list1": ["A", "B", "C"],
    "list2": [1, 2, 3],
}

myarg = sys.argv[1]
print len(lists[myarg])

You note you have 13 lists in your script - where you have lots of similar data (or data that needs to be handled in a similar way), it's a sign you want a data structure, rather than flat variables. It will make your life a lot easier.