Skipping every other element after the first

Question

I have the general idea of how to do this in Java  but I am learning Python and not sure how to do it    I need to implement a function that returns a list containing every other element of the list  starting with the first element   Thus far  I have and not sure how to do from here since I am just learning how for-loops in Python are different   def altElement a       b          for i in a          b append a       print b

User · Answer

Slice notation a start index end index step   return a   2    where start index defaults to 0 and end index defaults to the len a

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def skip elements elements      new list          i   0    for element in elements         if i 2  0           c elements i           new list append c         i  1   return new list

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def skip elements elements         Initialize variables     i   0     new list elements   2      return new list    Should be   a    c    e    g        print skip elements   a    b    c    d    e    f    g       Should be   Orange    Strawberry    Peach    print skip elements   Orange    Pineapple    Strawberry    Kiwi    Peach        Should be     print skip elements

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def skip elements elements         Initialize variables     new list          i   0        Iterate through the list     for words in elements            Does this element belong in the resulting list          if i  lt   len elements                 Add this element to the resulting list             new list insert i elements i             Increment i         i    2      return new list

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There are more ways than one to skin a cat  - Seba Smith   arr   list range 10     Range from 0-9    List comprehension  Range with conditional print  arr index  for index in range len arr   if index   2    0     List comprehension  Range with step print  arr index  for index in range 0  len arr   2      List comprehension  Enumerate with conditional print  item for index  item in enumerate arr  if index   2    0     List filter  Index in range print filter lambda index  index   2    0  range len arr       Extended slice print arr   2

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items   range 10  print items  gt  gt  gt   0  1  2  3  4  5  6  7  8  9  print items 1  2    every other item after the second  slight variation  gt  gt  gt   1  3  5  7  9

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Initialize variables new list      i   0   Iterate through the list for i in range len elements          Does this element belong in the resulting list      if i 2  0            Add this element to the resulting list         new list append elements i         Increment i     i   2  return new list

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b   a   2    This uses the extended slice syntax

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def skip elements elements         code goes here     new list        for index alpha in enumerate elements           if index 2  0              new list append alpha      return new list   print skip elements   quot a quot    quot b quot    quot c quot    quot d quot    quot e quot    quot f quot    quot g quot       print skip elements   Orange    Pineapple    Strawberry    Kiwi    Peach

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def altElement a       return a   2

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Using the for-loop like you have  one way is this   def altElement a       b          j   False     for i in a          j   not j         if j              b append i       print b   j just keeps switching between 0 and 1 to keep track of when to append an element to b

User · Answer

Or you can do it like this        def skip elements elements             Initialize variables         new list              i   0            Iterate through the list         for words in elements                 Does this element belong in the resulting list              if i  lt   len elements                     Add this element to the resulting list                 new list append elements i                 Increment i                 i    2          return new list      print skip elements   a    b    c    d    e    f    g       Should be   a    c    e    g       print skip elements   Orange    Pineapple    Strawberry    Kiwi    Peach       Should be   Orange    Strawberry    Peach       print skip elements        Should be

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def skip elements elements     new list        for index element in enumerate elements       if index    0        new list append element      elif  index   2     0         new list append element    return new list   Also can use for loop   enumerate           elif  index   2     0     Checking if number is even  not odd cause indexing starts from zero not 1

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Alternatively  you could do   for i in range 0  len a   2        do something   The extended slice notation is much more concise  though

[python] Skipping every other element after the first

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