Get column index from column name in python pandas

Question

In R when you need to retrieve a column index based on the name of the column you could do  idx  lt - which names my data   my colum name    Is there a way to do the same with pandas dataframes

User · Answer

Here is a solution through list comprehension  cols is the list of columns to get index for    df columns get loc c  for c in cols if c in df

User · Answer

Sure  you can use  get loc     In  45   df   DataFrame   pear    1 2 3    apple    2 3 4    orange    3 4 5     In  46   df columns Out 46   Index  apple  orange  pear   dtype object   In  47   df columns get loc  pear   Out 47   2   although to be honest I don t often need this myself   Usually access by name does what I want it to  df  pear    df   apple    orange     or maybe df columns isin   orange    pear      although I can definitely see cases where you d want the index number

User · Answer

In case you want the column name from the column location  the other way around to the OP question   you can use    gt  gt  gt  df columns get values   location    Using  DSM Example    gt  gt  gt  df   DataFrame   pear    1 2 3    apple    2 3 4    orange    3 4 5      gt  gt  gt  df columns  Index   apple    orange    pear    dtype  object     gt  gt  gt  df columns get values   1    orange    Other ways   df iloc   1  name  df columns location    thanks to  roobie-nuby for pointing that out in comments

User · Answer

how about this   df   DataFrame   pear    1 2 3    apple    2 3 4    orange    3 4 5    out   np argwhere df columns isin   apple    orange     ravel   print out   1 2

User · Answer

To modify DSM s answer a bit  get loc has some weird properties depending on the type of index in the current version of Pandas  1 1 5  so depending on your Index type you might get back an index  a mask  or a slice   This is somewhat frustrating for me because I don t want to modify the entire columns just to extract one variable s index  Much simpler is to avoid the function altogether  list df columns  index  pear    Very straightforward and probably fairly quick

User · Answer

DSM s solution works  but if you wanted a direct equivalent to which you could do  df columns    name  nonzero

User · Answer

When you might be looking to find multiple column matches  a vectorized solution using searchsorted method could be used  Thus  with df as the dataframe and query cols as the column names to be searched for  an implementation would be -  def column index df  query cols       cols   df columns values     sidx   np argsort cols      return sidx np searchsorted cols query cols sorter sidx     Sample run -  In  162   df Out 162       apple  banana  pear  orange  peach 0      8       3     4       4      2 1      4       4     3       0      1 2      1       2     6       8      1  In  163   column index df    peach    banana    apple    Out 163   array  4  1  0

User · Answer

For returning multiple column indices  I recommend using the pandas Index method get indexer  if you have unique labels  df   pd DataFrame   quot pear quot    1  2  3    quot apple quot    2  3  4    quot orange quot    3  4  5    df columns get indexer   pear    apple      Out  array  0  1   dtype int64   If you have non-unique labels in the index  columns only support unique labels  get indexer for  It takes the same args as get indeder  df   pd DataFrame        quot pear quot    1  2  3    quot apple quot    2  3  4    quot orange quot    3  4  5         index  0  1  1   df index get indexer for  0  1     Out  array  0  1  2   dtype int64   Both methods also support non-exact indexing with  f i  for float values taking the nearest value with a tolerance  If two indices have the same distance to the specified label or are duplicates  the index with the larger index value is selected  df   pd DataFrame        quot pear quot    1  2  3    quot apple quot    2  3  4    quot orange quot    3  4  5        index  0   9  1 1   df index get indexer  0  1     array   0  -1   dtype int64

[python] Get column index from column name in python pandas

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