Why is there no tuple comprehension in Python

Question

As we all know  there s list comprehension  like   i for i in  1  2  3  4     and there is dictionary comprehension  like   i j for i  j in  1   a   2   b   items      but   i for i in  1  2  3     will end up in a generator  not a tuple comprehension  Why is that   My guess is that a tuple is immutable  but this does not seem to be the answer

User · Answer

My best guess is that they ran out of brackets and didn t think it would be useful enough to warrent adding an  ugly  syntax

User · Answer

You can use a generator expression   tuple i for i in  1  2  3     but parentheses were already taken for     generator expressions

User · Answer

Since Python 3 5  you can also use splat   unpacking syntax to unpack a generator expresion     x for x in range 10

User · Answer

I believe it s simply for the sake of clarity  we do not want to clutter the language with too many different symbols  Also a tuple comprehension is never necessary  a list can just be used instead with negligible speed differences  unlike a dict comprehension as opposed to a list comprehension

User · Answer

As another poster macm mentioned  the fastest way to create a tuple from a generator is tuple  generator       Performance Comparison   List comprehension     python3 -m timeit  a    i for i in range 1000    10000 loops  best of 3  27 4 usec per loop  Tuple from list comprehension     python3 -m timeit  a   tuple  i for i in range 1000     10000 loops  best of 3  30 2 usec per loop  Tuple from generator     python3 -m timeit  a   tuple i for i in range 1000    10000 loops  best of 3  50 4 usec per loop  Tuple from unpacking     python3 -m timeit  a     i for i in range 1000     10000 loops  best of 3  52 7 usec per loop    My version of python     python3 --version Python 3 6 3     So you should always create a tuple from a list comprehension unless performance is not an issue

User · Answer

Raymond Hettinger  one of the Python core developers  had this to say about tuples in a recent tweet       python tip  Generally  lists are for looping  tuples for structs  Lists are homogeneous  tuples heterogeneous  Lists for variable length    This  to me  supports the idea that if the items in a sequence are related enough to be generated by a  well  generator  then it should be a list  Although a tuple is iterable and seems like simply a immutable list  it s really the Python equivalent of a C struct   struct       int a      char b      float c    foo   struct foo x     3   g   5 9      becomes in Python  x    3   g   5 9

User · Answer

Tuples cannot efficiently be appended like a list     So a tuple comprehension would need to use a list internally and then convert to a tuple     That would be the same as what you do now   tuple    comprehension

User · Answer

Parentheses do not create a tuple  aka one    two  is not a tuple  The only way around is either one    two   or one   tuple two   So a solution is   tuple i for i in myothertupleorlistordict

User · Answer

We can generate tuples from a list comprehension  The following one adds two numbers sequentially into a tuple and gives a list from numbers 0-9    gt  gt  gt  print k  0  1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35  36  37  38  39  40  41  42  43  44  45  46  47  48  49  50  51  52  53  54  55  56  57  58  59  60  61  62  63  64  65  66  67  68  69  70  71  72  73  74  75  76  77  78  79  80  81  82  83  84  85  86  87  88  89  90  91  92  93  94  95  96  97  98  99   gt  gt  gt  r   tuple k i i 2   for i in xrange 10  if not i 2   gt  gt  gt  print r   0  1    2  3    4  5    6  7    8  9

User · Answer

Comprehension works by looping or iterating over items and assigning them into a container  a Tuple is unable to receive assignments   Once a Tuple is created  it can not be appended to  extended  or assigned to  The only way to modify a Tuple is if one of its objects can itself be assigned to  is a non-tuple container   Because the Tuple is only holding a reference to that kind of object   Also - a tuple has its own constructor tuple   which you can give any iterator  Which means that to create a tuple  you could do   tuple i for i in  1 2 3

[python] Why is there no tuple comprehension in Python?

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