Getting a sublist of a Python list, with the given indices?

Question

I have a Python list, say a = [0,1,2,3,4,5,6]. I also have a list of indices, say b = [0,2,4,5]. How can I get the list of elements of a

Answer 1

You can use list comprehension to get that list:

c = [a[index] for index in b]
print c

This is equivalent to:

c= []
for index in b:
    c.append(a[index])
print c

Output:

[0,2,4,5]

Note:

Remember that some_list[index] is the notation used to access to an element of a list in a specific index.

Answer 2

Yet another alternative for better performance if that is important to you- it is by no means the most Pythonic but I am pretty sure it is the most efficient:

>>> list(filter(lambda x: a.index(x) in b, a))
[0, 2, 4, 5]

Note: You do not need to convert to a list in Python 2. However you do in Python 3 onwards (if any future visitors may have a similar issue).