How to get a list as user input and then iterate using the input. - Python 3.4

When you get user input into a, it is a string. When you are iterating through it in your example; you are iterating through the actual string 'list1'.

If you wanted to go through the items in the list you need to link them somehow.

Try this:

lists = {
'list1': [0,1,0,1,0,1],
'list2': [1,0,1,0,1,0]}

a = input("Which list do you want to search for?")
if a in lists:
    for item in lists[a]:
        print(item)
else:
    print("Don't have that list")

Note:

for item in lists[a]

That lists[a] references that list; you can do what you want with it now; like use range/len....

In case you are using Python3 (you must be, otherwise the code works fine),

a is a string, not the variable itself.

You can verify it doing

list1 = [0,1,0,1,0,1]
list2 = [1,0,1,0,1,0]
a = input("Which list do you want to search for?")
print(type(a))

which gives you

<class 'str'>

So you can try this instead:

for item in range(len(vars()[a])):
    print(item)

which produces

0
1
2
3
4
5

From the official docs:

vars([object])

Return the dict attribute for a module, class, instance, or any other object with a dict attribute. Objects such as modules and instances have an updateable dict attribute; however, other objects may have write restrictions on their dict attributes (for example, classes use a dictproxy to prevent direct dictionary updates). Without an argument, vars() acts like locals(). Note, the locals dictionary is only useful for reads since updates to the locals dictionary are ignored.

As an alternative, you can use eval

for item in range(len(eval(a))):
    print(item)

but it's not recommended (see the official docs) since

This function can also be used to execute arbitrary code

Note: there are several ways to solve this problem. For example, as pointed out below, you could decide which list to use by checking the input with an if and hard-code the list in either branch taken. The problem with this option is that it does not fit a higher/variable/dynamic number of lists.

Another approach could be to store the lists in a dictionary and look them up using the input key, as suggested in another answer. This one and mine have the benefit of being able to handle any number of lists, not just a few and even lists created dynamically in the namespace.