Is string.join faster with tuples or a list?

Question

If I have the choice between

''.join( ['a', 'b'] )

and

''.join( ('a', 'b') )

which one should I use (which one is faster)? Does it matter?

Answer 1

They are almost equivalent and you can always time your code using timeit module:

In [145]: small_lis,small_tup = ['a','b']*10, ('a','b')*10

In [146]: avg_lis,avg_tup = ['a','b']*1000, ('a','b')*1000

In [147]: huge_lis,huge_tup = ['a','b']*10**6, ('a','b')*10**6

Timing results when number of items are 20:

>>> %timeit ''.join(small_lis)
1000000 loops, best of 3: 987 ns per loop

>>> %timeit ''.join(small_tup)
1000000 loops, best of 3: 1 us per loop

Average size(2000 items):

>>> %timeit ''.join(avg_lis)
10000 loops, best of 3: 71.5 us per loop

>>> %timeit ''.join(avg_tup)
10000 loops, best of 3: 72.8 us per loop

Huge size (2* 10**6 items):

>>> %timeit ''.join(huge_lis)
1 loops, best of 3: 79.9 ms per loop

>>> %timeit ''.join(huge_tup)
1 loops, best of 3: 77.5 ms per loop