creating a new list with subset of list using index in python

Question

A list   a     a    b    c   3  4   d   6  7  8    I want a list using a subset of a using a 0 2  a 4   a 6      that is I want a list   a    b   4  6  7  8

User · Answer

Suppose  a     a    b    c   3  4   d   6  7  8    and the list of indexes is stored in  b   0  1  2  4  6  7  8    then a simple one-line solution will be  c    a i  for i in b

User · Answer

The following definition might be more efficient than the first solution proposed  def new list from intervals original list   intervals       n   sum j - i for i  j in intervals      new list    None    n     index   0     for i  j in intervals           for k in range i  j                new list index    original list k              index    1      return new list   then you can use it like below  new list   new list from intervals original list   0 2    4 5    6  len original list

User · Answer

Try new list   a 0 2     a 4     a 6     Or more generally  something like this   from itertools import chain new list   list chain a 0 2    a 4    a 6       This works with other sequences as well  and is likely to be faster   Or you could do this   def chain elements or slices  elements or slices       new list          for i in elements or slices          if isinstance i  list               new list extend i          else              new list append i      return new list  new list   chain elements or slices a 0 2   a 4   a 6      But beware  this would lead to problems if some of the elements in your list were themselves lists  To solve this  either use one of the previous solutions  or replace a 4  with a 4 5   or more generally a n  with a n n 1

[python] creating a new list with subset of list using index in python

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