Convert a list to a dictionary in Python

Question

Let s say I have a list a in Python whose entries conveniently map to a dictionary  Each even element represents the key to the dictionary  and the following odd element is the value  for example   a     hello   world   1   2     and I d like to convert it to a dictionary b  where   b  hello      world  b  1      2    What is the syntactically cleanest way to accomplish this

User · Accepted Answer

b   dict zip a   2   a 1  2      If a is large  you will probably want to do something like the following  which doesn t make any temporary lists like the above   from itertools import izip i   iter a  b   dict izip i  i     In Python 3 you could also use a dict comprehension  but ironically I think the simplest way to do it will be with range   and len    which would normally be a code smell   b    a i   a i 1  for i in range 0  len a   2     So the iter   izip   method is still probably the most Pythonic in Python 3  although as EOL notes in a comment  zip   is already lazy in Python 3 so you don t need izip     i   iter a  b   dict zip i  i     If you want it on one line  you ll have to cheat and use a semicolon    -

User · Answer

Something i find pretty cool  which is that if your list is only 2 items long   ls     a    b   dict  ls    gt  gt  gt    a   b     Remember  dict accepts any iterable containing an iterable where each item in the iterable must itself be an iterable with exactly two objects

User · Answer

I am not sure if this is pythonic  but seems to work  def alternate list a      return a   2   a 1  2   key list value list   alternate list a  b   dict zip key list value list

User · Answer

I am also very much interested to have a one-liner for this conversion  as far such a list is the default initializer for hashed in Perl   Exceptionally comprehensive answer is given in this thread -   python convert list to dictionary   Mine one I am newbie in Python   using Python 2 7 Generator Expressions  would be   dict  a i   a i   1   for i in range 0  len a  - 1  2

User · Answer

You can use a dict comprehension for this pretty easily   a     hello   world   1   2    my dict    item   a index 1  for index  item in enumerate a  if index   2    0    This is equivalent to the for loop below   my dict      for index  item in enumerate a       if index   2    0          my dict item    a index 1

User · Answer

x  a a index x  1  for x in a if a index x    2   0   result     hello    world    1    2

User · Answer

May not be the most pythonic  but   gt  gt  gt  b       gt  gt  gt  for i in range 0  len a   2           b a i     a i 1

User · Answer

You can also do it like this  string to list conversion here  then conversion to a dictionary       string list           Hello World     Goodbye Night     Great Day     Final Sunset         split        string list   dict zip string list   2  string list 1  2         print string list

User · Answer

Simple answer  Another option  courtesy of Alex Martelli - source    dict x i i 2  for i in range 0  len x   2       Related note  If you have this   a     bi   double   duo   two     and you want this  each element of the list keying a given value  2 in this case       bi  2  double  2  duo  2  two  2    you can use    gt  gt  gt  dict  k 2  for k in a    double   2   bi   2   two   2   duo   2

User · Answer

You can do it pretty fast without creating extra arrays  so this will work even for very large arrays   dict izip    iter a   2      If you have a generator a  even better   dict izip    a  2      Here s the rundown   iter h      create an iterator from the array  no copies here    2        creates an array with two copies of the same iterator  the trick izip        consumes the two iterators creating a tuple dict        puts the tuples into key value of the dictionary

User · Answer

try below code      gt  gt  gt  d2   dict    one  1     two   2     three   3       gt  gt  gt  d2         three   3   two   2   one   1

User · Answer

You can also try this approach save the keys and values in different list and then use dict method  data   test1    1    test2    2    test3    3    test4    4    keys    values    for i j in enumerate data       if i 2  0          keys append j      else          values append j   print dict zip keys values      output     test3    3    test1    1    test2    2    test4    4

[python] Convert a list to a dictionary in Python

Examples related to python

Examples related to list

Examples related to dictionary