how do I insert a column at a specific column index in pandas

Question

Can I insert a column at a specific column index in pandas    import pandas as pd df   pd DataFrame   l    a   b   c   d     v   1 2 1 2    df  n     0   This will put column n as the last column of df  but isn t there a way to tell df to put n at the beginning

User · Answer

df insert loc  column name  value   This will work if there is no other column with the same name  If a column  with your provided name already exists in the dataframe  it will raise a ValueError  You can pass an optional parameter allow duplicates with True value to create a new column with already existing column name  Here is an example             df   pd DataFrame   b    1  2    c    3 4            df        b  c     0  1  3     1  2  4         df insert 0   a   -1          df        a  b  c     0 -1  1  3     1 -1  2  4         df insert 0   a   -2      Traceback  most recent call last         File     line 1  in        File  C  Python39 lib site-packages pandas core frame py   line 3760  in insert         self  mgr insert loc  column  value  allow duplicates allow duplicates        File  C  Python39 lib site-packages pandas core internals managers py   line 1191  in insert         raise ValueError f cannot insert  item   already exists       ValueError  cannot insert a  already exists         df insert 0   a   -2   allow duplicates   True          df        a  a  b  c     0 -2 -1  1  3     1 -2 -1  2  4

User · Answer

You could try to extract columns as list  massage this as you want  and reindex your dataframe    gt  gt  gt  cols   df columns tolist    gt  gt  gt  cols    cols -1   cols  -1    or whatever change you need  gt  gt  gt  df reindex columns cols      n  l  v 0  0  a  1 1  0  b  2 2  0  c  1 3  0  d  2   EDIT  this can be done in one line   however  this looks a bit ugly  Maybe some cleaner proposal may come      gt  gt  gt  df reindex columns   n   df columns  -1  tolist        n  l  v 0  0  a  1 1  0  b  2 2  0  c  1 3  0  d  2

User · Answer

Here is a very simple answer to this only one line    You can do that after you added the  n  column into your df as follows    import pandas as pd df   pd DataFrame   l    a   b   c   d     v   1 2 1 2    df  n     0  df     l   v   n 0   a   1   0 1   b   2   0 2   c   1   0 3   d   2   0    here you can add the below code and it should work  df   df list  nlv    df      n   l   v 0   0   a   1 1   0   b   2 2   0   c   1 3   0   d   2    However  if you have words in your columns names instead of letters  It should include two brackets around your column names    import pandas as pd df   pd DataFrame   Upper    a   b   c   d     Lower   1 2 1 2    df  Net     0 df  Mid     2 df  Zsore     2  df      Upper   Lower   Net Mid Zsore 0   a       1       0   2   2 1   b       2       0   2   2 2   c       1       0   2   2 3   d       2       0   2   2    here you can add below line and it should work  df   df list   Mid   Upper    Lower    Net   Zsore     df     Mid  Upper   Lower   Net Zsore 0   2   a       1       0   2 1   2   b       2       0   2 2   2   c       1       0   2 3   2   d       2       0   2

User · Answer

If you want a single value for all rows   df insert 0  name of column      df  name of column     value   Edit   You can also   df insert 0  name of column  value

User · Answer

see docs  http   pandas pydata org pandas-docs stable generated pandas DataFrame insert html  using loc   0 will insert at the beginning  df insert loc  column  value      df   pd DataFrame   B    1  2  3    C    4  5  6     df Out      B  C 0  1  4 1  2  5 2  3  6  idx   0 new col    7  8  9     can be a list  a Series  an array or a scalar    df insert loc idx  column  A   value new col   df Out      A  B  C 0  7  1  4 1  8  2  5 2  9  3  6

[python] how do I insert a column at a specific column index in pandas?

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