Accessing a value in a tuple that is in a list

Question

1 2    2 3    4 5    3 4    6 7    6 7    3 8     How do I return the 2nd value from each tuple inside this list   Desired output    2  3  5  4  7  7  8

User · Answer

a     0 2    4 3    9 9    10 -1   print list map lambda item  item 1   a

User · Answer

You can also use sequence unpacking with zip   L     1 2   2 3   4 5   3 4   6 7   6 7   3 8       res   zip  L   print res      2  3  5  4  7  7  8    This also creates a tuple   from the discarded first elements  Extracting only the second is possible  but more verbose   from itertools import islice  res   next islice zip  L   1  None

User · Answer

With a list comprehension    x 1  for x in L

User · Answer

Ignacio s answer is what you want  However  as someone also learning Python  let me try to dissect it for you    As mentioned  it is a list comprehension  covered in DiveIntoPython3  for example   Here are a few points    x 1  for x in L    Notice the    s around the line of code  These are what define a list  This tells you that this code returns a list  so it s of the list type  Hence  this technique is called a  list comprehension   L is your original list  So you should define L     1 2   2 3   4 5   3 4   6 7   6 7   3 8   prior to executing the above code  x is a variable that only exists in the comprehension - try to access x outside of the comprehension  or type type x  after executing the above line and it will tell you NameError  name  x  is not defined  whereas type L  returns  lt class  list  gt   x 1  points to the second item in each of the tuples whereas x 0  would point to each of the first items  So this line of code literally reads  return the second item in a tuple for all tuples in list L     It s tough to tell how much you attempted the problem prior to asking the question  but perhaps you just weren t familiar with comprehensions  I would spend some time reading through Chapter 3 of DiveIntoPython  or any resource on comprehensions  Good luck

User · Answer

A list comprehension is absolutely the way to do this  Another way that should be faster is map and itemgetter   import operator  new list   map operator itemgetter 1   old list    In response to the comment that the OP couldn t find an answer on google  I ll point out a super naive way to do it   new list      for item in old list      new list append item 1     This uses    Declaring a variable to reference an empty list  A for loop  Calling the append method on a list    If somebody is trying to learn a language and can t put together these basic pieces for themselves  then they need to view it as an exercise and do it themselves even if it takes twenty hours   One needs to learn how to think about what one wants and compare that to the available tools  Every element in my second answer should be covered in a basic tutorial  You cannot learn to program without reading one

User · Answer

OR you can use pandas    gt  gt  gt  import pandas as pd  gt  gt  gt  L     1 2   2 3   4 5   3 4   6 7   6 7   3 8    gt  gt  gt  df pd DataFrame L   gt  gt  gt  df 1  0    2 1    3 2    5 3    4 4    7 5    7 6    8 Name  1  dtype  int64  gt  gt  gt  df 1  tolist    2  3  5  4  7  7  8   gt  gt  gt     Or numpy    gt  gt  gt  import numpy as np  gt  gt  gt  L     1 2   2 3   4 5   3 4   6 7   6 7   3 8    gt  gt  gt  arr np array L   gt  gt  gt  arr T 1  array  2  3  5  4  7  7  8    gt  gt  gt  arr T 1  tolist    2  3  5  4  7  7  8   gt  gt  gt

[python] Accessing a value in a tuple that is in a list

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