How to remove n from a list element

Question

I m trying to get Python to a read line from a  txt file and write the elements of the first line into a list  The elements in the file were tab- separated so I used split   t   to separate the elements  Because the  txt file has a lot of elements I saved the data found in each line into a separate list   The problem I currently have is that it s showing each list like this     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n     How can I remove  n from the last element of the list and make it just  7 3

User · Answer

from this link   you can use rstrip   method  Example  mystring    hello n      print mystring rstrip   n

User · Answer

You could do -  DELIMITER     t  lines   list   for line in open  file txt        lines append line strip   split DELIMITER     The lines has got all the contents of your file    One could also use list comprehensions to make this more compact   lines     line strip   split DELIMITER  for line in open  file txt

User · Answer

Since the OP s question is about stripping the newline character from the last element  I would reset it with the list -1  rstrip      gt  gt  gt  the list     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n    gt  gt  gt  the list -1    ls -1  rstrip    gt  gt  gt  the list   Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     It s O 1

User · Answer

You access the last element of the set and then store the value in a variable   So you have   fileName    7 3 n    then just do   fileName strip     which will leave you with 7 3  Then store that value back in the last element of the set    You can use lstrip   or rstrip   to remove just the left or right side

User · Answer

As an alternate method  if you know that there are no spaces in your data  which it seems is the case  you can use split    with no arguments   This splits on white space and uses a more efficient algorithm than the other version of split  It also strips whitespace from both ends   line   line split     And that s it

User · Answer

From Python3 onwards  map no longer returns a list but a mapObject  thus the answer will look something like   gt  gt  gt  map lambda x x strip   l   lt map object at 0x7f00b1839fd0 gt    You can read more about it on What   s New In Python 3 0      map   and filter   return iterators  If you really need a list  a quick fix is e g  list map         So now what are the ways of getting trough this     Case 1 - The list call over map with a lambda  map returns an iterator  list is a function that can convert an iterator to a list  Hence you will need to wrap a list call around map  So the answer now becomes    gt  gt  gt  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n    gt  gt  gt  list map lambda x x strip   l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     Very good  we get the output  Now we check the amount of time it takes for this piece of code to execute     python3 -m timeit  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n   list map lambda x x strip   l    100000 loops  best of 3  2 22 usec per loop   2 22 microseconds  That is not so bad  But are there more efficient ways     Case 2 - The list call over map withOUT a lambda  lambda is frowned upon by many in the Python community  including Guido   Apart from that it will greatly reduce the speed of the program  Hence we need to avoid that as much as possible  The toplevel function str strip  Comes to our aid here    The map can be re-written without using lambda using str strip as   gt  gt  gt  list map str strip l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     And now for the times      python3 -m timeit  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n   list map str strip l    1000000 loops  best of 3  1 38 usec per loop   Fantastic  You can see the efficiency differences between the two ways  It is nearly 60  faster  Thus the approach without using a lambda is a better choice here     Case 3 - Following Guidelines  The Regular way  Another important point from What   s New In Python 3 0 is that it advices us to avoid map where possible      Particularly tricky is map   invoked for the side effects of the   function  the correct transformation is to use a regular for loop    since creating a list would just be wasteful     So we can solve this problem without a map by using a regular for loop    The trivial way of solving  the brute-force  would be -   gt  gt  gt  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n    gt  gt  gt  final list       gt  gt  gt  for i in l          final list append i strip          gt  gt  gt  final list   Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     The timing setup  def f        l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n       final list          for i in l           final list append i strip    import timeit print min timeit repeat  f     from   main   import f       And the result    1 5322505849981098   As you can see the brute-force is a bit slower here  But it is definitely more readable to a common programmer than a map clause      Case 4 - List Comprehensions  A list comprehension here is also possible and is the same as in Python2    gt  gt  gt   i strip   for i in l    Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     Now for the timings     python3 -m timeit  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n    i strip   for i in l   1000000 loops  best of 3  1 28 usec per loop   As you can see the list-comprehension is more effective than map  even that without a lambda   Hence the thumb rule in Python3 is to use a list comprehension instead of map    Case 5 - In-Place mechanisms and Space Efficiency  T-M-T   A final way is to make the changes in-place within the list itself  This will save a lot of memory space  This can be done using enumerate    gt  gt  gt  l     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n    gt  gt  gt  for i s in enumerate l           l i    s strip         gt  gt  gt  l   Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3     The timing result would be 1 4806894720022683  But however this way is space effective      Conclusion  A comparitive list of timings  Both Python 3 4 3 and Python 3 5 0    ----------------------------------------------------  Case  method            Py3 4  Place  Py3 5  Place   ---- ----------------- ------- ----- ------- -----    1    map with lambda   2 22u   5     2 85u   5       2    map w o lambda    1 38u   2     2 00u   2       3    brute-force       1 53u   4     2 22u   4       4    list comp         1 28u   1     1 25u   1       5    in-place          1 48u   3     2 14u   3     ----------------------------------------------------   Finally note that the list-comprehension is the best way and the map using lambda is the worst  But again --- ONLY IN PYTHON3

User · Answer

It sounds like you want something like the Perl chomp   function   That s trivial to do in Python   def chomp s       return s  -1  if s endswith   n   else s       assuming you re using Python 2 6 or later   Otherwise just use the slightly more verbose   def chomp s       if s endwith   n            return s  -1      else          return s   If you want to remove all new lines from the end of a string  in the odd case where one might have multiple trailing newlines for some reason    def chomps s       return s rstrip   n     Obviously you should never see such a string returned by any normal Python file object s readline   nor readlines   methods   I ve seen people blindly remove the last characters  using s  -1  slicing  from the results of file readline   and similar functions   This is a bad idea because it can lead to an error on the last line of the file  in the case where a file ends with anything other than a newline    At first you might be lulled into a false sense of security when blindly stripping final characters off lines you ve read   If you use a normal text editor to create your test suite files you ll have a newline silently added to the end of the last line by most of them   To create a valid test file use code something like   f   open  sometest txt    w   f write  some text   f close         and then if you re-open that file and use the readline   or readlines   file methods on it you ll find that the text is read without the trailing newline   This failure to account for text files ending in non-newline characters has plagued many UNIX utilities and scripting languages for many years   It s a stupid corner base bug that creeps into code just often enough to be a pest but not often enough for people to learn from it   We could argue that  text  files without the ultimate newline are  corrupt  or non-standard  and that may be valid for some programming specifications   However  it s all too easy to ignore corner cases in our coding and have that ignorance bite people who are depending on your code later   As my wife says  when it comes to programming     practice safe hex

User · Answer

Using list comprehension   myList     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n      el strip    for el in myList

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str strip   removes the whitespace characters  you can also pass custom characters as argument to strip  The strip function removes the whitespace custom characters on both ends of the string  lstrip   and rstrip   are left strip and right strip functions resp   Eg   test str    Vishaka n   test str   test str strip     test str s now Vishaka

User · Answer

If you want to remove  n from the last element only  use this   t -1    t -1  strip     If you want to remove  n from all the elements  use this   t   map lambda s  s strip    t    You might also consider removing  n before splitting the line   line   line strip     split line

User · Answer

This will also work   f open  in txt   r        for line in f              parline   line  -1  split

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new list     Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3 n   for i in range len new list        new list i  new list i  replace   n      print new list    Output Will be like this    Name1    7 3    6 9    6 6    6 6    6 1    6 4    7 3

User · Answer

To handle many newline delimiters  including character combinations like  r n  use splitlines  Combine join and splitlines to remove replace all newlines from a string s      join s splitlines      To remove exactly one trailing newline  pass True as the keepends argument to retain the delimiters  removing only the delimiters on the last line    def chomp s       if len s           lines   s splitlines True          last   lines pop           return    join lines   last splitlines        else          return

User · Answer

I had this issue and solved it using the chomp function described above   def chomp s       return s  -1  if s endswith   n   else s  def trim newlines slist       for i in range len slist            slist i    chomp slist i       return slist       names   theFile readlines   names   trim newlines names

User · Answer

This works to take out the  n  new line  off a item in a list it just takes the first item in string off  def remove end s       templist        for i in s          templist append i      return templist 0

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