Get the first element of each tuple in a list in Python

Question

An SQL query gives me a list of tuples  like this     elt1  elt2    elt1  elt2    elt1  elt2    elt1  elt2    elt1  elt2          I d like to have all the first elements of each tuple  Right now I use this   rows   cur fetchall   res list      for row in rows      res list     row 0     But I think there might be a better syntax to do it  Do you know a better way

User · Answer

You can use list comprehension   res list    i 0  for i in rows    This should make the trick

User · Answer

If you don t want to use list comprehension by some reasons  you can use map and operator itemgetter    gt  gt  gt  from operator import itemgetter  gt  gt  gt  rows     1  2    3  4    5  6    gt  gt  gt  map itemgetter 1   rows   2  4  6   gt  gt  gt

User · Answer

res list    x 0  for x in rows    c f  http   docs python org 3 tutorial datastructures html list-comprehensions  For a discussion on why to prefer comprehensions over higher-order functions such as map  go to http   www artima com weblogs viewpost jsp thread 98196

User · Answer

The functional way of achieving this is to unzip the list using   sample     2  9    2  9    8  9    10  9    23  26    1  9    43  44   first snd   zip  sample  print first snd     2  2  8  10  23  1  43   9  9  9  9  26  9  44

User · Answer

Use a list comprehension   res list    x 0  for x in rows    Below is a demonstration    gt  gt  gt  rows     1  2    3  4    5  6    gt  gt  gt   x 0  for x in rows   1  3  5   gt  gt  gt      Alternately  you could use unpacking instead of x 0    res list    x for x   in rows    Below is a demonstration    gt  gt  gt  lst     1  2    3  4    5  6    gt  gt  gt   x for x   in lst   1  3  5   gt  gt  gt    Both methods practically do the same thing  so you can choose whichever you like

[python] Get the first element of each tuple in a list in Python

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