Converting a list of tuples into a simple flat list [duplicate]

Question

Possible Duplicate:
How do I convert a tuple of tuples to a one-dimensional list using list comprehension?

Let's say I have the following list of tuples:

[(1,2), (1,3), (1,4), (1,5), (1,6)] 

I am trying to convert it to a simple list like I have below:

[1,2,1,3,1,4,1,5,1,6] 

How do I convert it to a simple list like the one above without having to iterate through each element and add the items one by one to another list?

Are there any fast and efficient ways to do this without actually iterating through the original list of tuples, or is there some built-in function/method to do this?

Answer 1

lst = [(1,2), (1,3), (1,4), (1,5), (1,6)]  import itertools list(itertools.chain(*lst)) # [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] 

Alternatively:

[e for l in lst for e in l] # [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] 

Answer 2

“Fundamentally, which one is faster? Using the "itertools" module, or using a list comprehension? I'm basically trying to improve my computation speed here.” - @davidadamojr

I've been doing some tests and I find that the code below is actually faster.

list_ = [(1, 2), (1, 3), (1, 4), (1, 5), (1, 6)] list(sum(list_, ())) 

Someone correct me if I'm wrong.

Here are some tests below.

>>> list_ = [(1, 2), (1, 3), (1, 4), (1, 5), (1, 6)] >>>  >>> operation_1 = lambda: [tuple_item for tuple_ in list_ for tuple_item in tuple_] >>> def operation_2 ():         final_list = []         for tuple_ in list_:             for tuple_item in tuple_:                 final_list.append(tuple_item)         return final_list  >>> operation_3 = lambda: reduce(list.__add__, map(list, list_)) >>> def operation_4 ():         import itertools         return list(itertools.chain(*list_))  >>> operation_5 = lambda: list(sum(list_, ())) >>>  >>> operation_1() [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] >>> operation_2() [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] >>> operation_3() [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] >>> operation_4() [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] >>> operation_5() [1, 2, 1, 3, 1, 4, 1, 5, 1, 6] >>>  >>> import timeit >>>  >>> print('operation_1 completed in %s seconds.' % (timeit.timeit(operation_1))) operation_1 completed in 1.57890490223 seconds. >>> print('operation_2 completed in %s seconds.' % (timeit.timeit(operation_2))) operation_2 completed in 2.90350501659 seconds. >>> print('operation_3 completed in %s seconds.' % (timeit.timeit(operation_3))) operation_3 completed in 5.08437990236 seconds. >>> print('operation_4 completed in %s seconds.' % (timeit.timeit(operation_4))) operation_4 completed in 3.85125378138 seconds. >>> print('operation_5 completed in %s seconds.' % (timeit.timeit(operation_5))) operation_5 completed in 1.2623826489 seconds.