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

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.

Something different...

>>> a = range(7)
>>> b = [0,2,4,5]
>>> import operator
>>> operator.itemgetter(*b)(a)
(0, 2, 4, 5)

The itemgetter function takes one or more keys as arguments, and returns a function which will return the items at the given keys in its argument. So in the above, we create a function which will return the items at index 0, index 2, index 4, and index 5, then apply that function to a.

It appears to be quite a bit faster than the equivalent list comprehension

In [1]: import operator

In [2]: a = range(7)

In [3]: b = [0,2,4,5]

In [4]: %timeit operator.itemgetter(*b)(a)
1000000 loops, best of 3: 388 ns per loop

In [5]: %timeit [ a[i] for i in b ]
1000000 loops, best of 3: 415 ns per loop

In [6]: f = operator.itemgetter(*b)

In [7]: %timeit f(a)
10000000 loops, best of 3: 183 ns per loop

As for why itemgetter is faster, the comprehension has to execute extra Python byte codes.

In [3]: def f(a,b): return [a[i] for i in b]

In [4]: def g(a,b): return operator.itemgetter(*b)(a)

In [5]: dis.dis(f)
  1           0 BUILD_LIST               0
              3 LOAD_FAST                1 (b)
              6 GET_ITER
        >>    7 FOR_ITER                16 (to 26)
             10 STORE_FAST               2 (i)
             13 LOAD_FAST                0 (a)
             16 LOAD_FAST                2 (i)
             19 BINARY_SUBSCR
             20 LIST_APPEND              2
             23 JUMP_ABSOLUTE            7
        >>   26 RETURN_VALUE

While itemgetter is a single call implemented in C:

In [6]: dis.dis(g)
  1           0 LOAD_GLOBAL              0 (operator)
              3 LOAD_ATTR                1 (itemgetter)
              6 LOAD_FAST                1 (b)
              9 CALL_FUNCTION_VAR        0
             12 LOAD_FAST                0 (a)
             15 CALL_FUNCTION            1
             18 RETURN_VALUE