Index all except one item in python

Question

Is there a simple way to index all elements of a list  or array  or whatever  except for a particular index   E g      mylist 3  will return the item in position 3 milist  3  will return the whole list except for 3

User · Answer

Use np delete   It does not actually delete anything inplace  Example   import numpy as np a   np array   1 4   5 7   3 1                                              a  array   1  4                5  7                3  1     ind   np array  0 1                                                         ind  array  0  1      a ind   array   1  4                     5  7     all except index   np delete a  ind  axis 0                                                  all except index  array   3  1       a   still the same   array   1  4                                  5  7                                  3  1

User · Answer

The simplest way I found was  mylist  x    mylist x 1    that will produce your mylist without the element at index x  Example mylist    0  1  2  3  4  5  x   3 mylist  x    mylist x 1    Result produced mylist    0  1  2  4  5

User · Answer

I m going to provide a functional  immutable  way of doing it    The standard and easy way of doing it is to use slicing   index to remove   3 data     range 5   new data   data  index to remove    data index to remove   1    print f data   data   new data   new data      Output   data   0  1  2  3  4   new data   0  1  2  4   Use list comprehension   data     range 5   new data    v for i  v in enumerate data  if i    index to remove   print f data   data   new data   new data       Output   data   0  1  2  3  4   new data   0  1  2  4   Use filter function   index to remove   3 data     range 5   new data     filter lambda i  i    index to remove  data     Output   data   0  1  2  3  4   new data   0  1  2  4   Using masking  Masking is provided by itertools compress function in the standard library   from itertools import compress  index to remove   3 data     range 5   mask    1    len data  mask index to remove    0 new data     compress data  mask    print f data   data   mask   mask   new data   new data      Output   data   0  1  2  3  4   mask   1  1  1  0  1   new data   0  1  2  4   Use itertools filterfalse function from Python standard library  from itertools import filterfalse  index to remove   3 data     range 5   new data     filterfalse lambda i  i    index to remove  data    print f data   data   new data   new data      Output   data   0  1  2  3  4   new data   0  1  2  4

User · Answer

If you don t know the index beforehand here is a function that will work  def reverse index l  index       try          l pop index          return l     except IndexError          return False

User · Answer

Note that if variable is list of lists  some approaches would fail  For example   v1     range 3   for x in range 4   v2   v1  3  v1 4     this fails v2   For the general case  use  removed index   1 v1     range 3   for x in range 4   v2    x for i x in enumerate v1  if x  removed index  v2

User · Answer

gt  gt  gt  l   range 1 10   gt  gt  gt  l  1  2  3  4  5  6  7  8  9   gt  gt  gt  l  2    1  2   gt  gt  gt  l 3    4  5  6  7  8  9   gt  gt  gt  l  2    l 3    1  2  4  5  6  7  8  9   gt  gt  gt     See also  Explain Python  39 s slice notation

User · Answer

If you are using numpy  the closest  I can think of is using a mask   gt  gt  gt  import numpy as np  gt  gt  gt  arr   np arange 1 10   gt  gt  gt  mask   np ones arr shape dtype bool   gt  gt  gt  mask 5  0  gt  gt  gt  arr mask  array  1  2  3  4  5  7  8  9     Something similar can be achieved using itertools without numpy   gt  gt  gt  from itertools import compress  gt  gt  gt  arr   range 1 10   gt  gt  gt  mask    1  len arr   gt  gt  gt  mask 5  0  gt  gt  gt  list compress arr mask    1  2  3  4  5  7  8  9

User · Answer

If you want to cut out the last or the first do this  list     quot This quot    quot is quot    quot a quot    quot list quot   listnolast   list  -1  listnofirst   list 1     If you change 1 to 2 the first 2 characters will be removed not the second  Hope this still helps

User · Answer

For a list  you could use a list comp   For example  to make b a copy of a without the 3rd element   a   range 10    -1                           9  8  7  6  5  4  3  2  1  0  b    x for i x in enumerate a  if i  3       9  8  7  5  4  3  2  1  0    This is very general  and can be used with all iterables  including numpy arrays   If you replace    with     b will be an iterator instead of a list   Or you could do this in-place with pop   a   range 10    -1        a    9  8  7  6  5  4  3  2  1  0  a pop 3                   a    9  8  7  5  4  3  2  1  0    In numpy you could do this with a boolean indexing   a   np arange 9  -1  -1        a   array  9  8  7  6  5  4  3  2  1  0   b   a np arange len a    3     b   array  9  8  7  5  4  3  2  1  0     which will  in general  be much faster than the list comprehension listed above

[python] Index all except one item in python

Examples related to python

Examples related to list

Examples related to numpy

Examples related to indexing

[python] Index all *except* one item in python

Examples related to python

Examples related to list

Examples related to numpy

Examples related to indexing

[python] Index all except one item in python