Python Pandas Get index of rows which column matches certain value

Question

Given a DataFrame with a column  BoolCol   we want to find the indexes of the DataFrame in which the values for  BoolCol     True  I currently have the iterating way to do it  which works perfectly   for i in range 100 3000       if df iloc i   BoolCol     True           print i df iloc i   BoolCol     But this is not the correct panda s way to do it  After some research  I am currently using this code   df df  BoolCol      True  index tolist     This one gives me a list of indexes  but they dont match  when I check them by doing   df iloc i   BoolCol     The result is actually False    Which would be the correct Pandas way to do this

User · Answer

If you want to use your dataframe object only once  use   df  BoolCol   loc lambda x  x  True  index

User · Answer

df iloc i  returns the ith row of df  i does not refer to the index label  i is a 0-based index   In contrast  the attribute index returns actual index labels  not numeric row-indices   df index df  BoolCol      True  tolist     or equivalently   df index df  BoolCol    tolist     You can see the difference quite clearly by playing with a DataFrame with a non-default index that does not equal to the row s numerical position   df   pd DataFrame   BoolCol    True  False  False  True  True           index  10 20 30 40 50    In  53   df Out 53       BoolCol 10    True 20   False 30   False 40    True 50    True   5 rows x 1 columns   In  54   df index df  BoolCol    tolist   Out 54    10  40  50      If you want to use the index    In  56   idx   df index df  BoolCol     In  57   idx Out 57   Int64Index  10  40  50   dtype  int64     then you can select the rows using loc instead of iloc   In  58   df loc idx  Out 58       BoolCol 10    True 40    True 50    True   3 rows x 1 columns      Note that loc can also accept boolean arrays   In  55   df loc df  BoolCol    Out 55       BoolCol 10    True 40    True 50    True   3 rows x 1 columns      If you have a boolean array  mask  and need ordinal index values  you can compute them using np flatnonzero   In  110   np flatnonzero df  BoolCol    Out 112   array  0  3  4     Use df iloc to select rows by ordinal index   In  113   df iloc np flatnonzero df  BoolCol     Out 113       BoolCol 10    True 40    True 50    True

User · Answer

Simple way is to reset the index of the DataFrame prior to filtering   df reset   df reset index   df reset df reset  BoolCol    index tolist     Bit hacky  but it s quick

User · Answer

First you may check query when the target column is type bool   PS  about how to use it please check link    df query  BoolCol   Out 123        BoolCol 10     True 40     True 50     True   After we filter the original df by the Boolean column we can pick the index    df df query  BoolCol   df index Out 125   Int64Index  10  40  50   dtype  int64       Also pandas have nonzero  we just select the position of True row and using it slice the DataFrame or index   df index df BoolCol nonzero   0   Out 128   Int64Index  10  40  50   dtype  int64

User · Answer

I extended this question that is how to gets the row  columnand value of all matches value   here is solution   import pandas as pd import numpy as np   def search coordinate df data  pd DataFrame  search set  set  - gt  list      nda values   df data values     tuple index   np where np isin nda values   e for e in search set        return   row  col  nda values row  col   for row  col in zip tuple index 0   tuple index 1      if   name         main         test datas      cat    dog                            goldfish        kitten                        Puppy    hamster    mouse                           df data   pd DataFrame test datas      print df data      result list   search coordinate df data    dog    Puppy        print f  n n  row   lt 4    col   lt 4    name   gt 10         print f  row  lt 4   col  lt 4   name  gt 10    for row  col  name in result list    Output             0        1       2 0       cat      dog         1  goldfish           kitten 2     Puppy  hamster   mouse   row  col        name 0    1           dog 2    0         Puppy

User · Answer

Can be done using numpy where   function   import pandas as pd import numpy as np  In  716   df   pd DataFrame   gene name     SLC45A1    NECAP2    CLIC4    ADC    AGBL4      BoolCol    False  True  False  True  True            index list  abcde     In  717   df Out 717      BoolCol gene name a   False   SLC45A1 b    True    NECAP2 c   False     CLIC4 d    True       ADC e    True     AGBL4  In  718   np where df  BoolCol      True  Out 718    array  1  3  4      In  719   select indices   list np where df  BoolCol      True  0    In  720   df iloc select indices  Out 720      BoolCol gene name b    True    NECAP2 d    True       ADC e    True     AGBL4   Though you don t always need index for a match  but incase if you need   In  796   df iloc select indices  index Out 796   Index  u b   u d   u e    dtype  object    In  797   df iloc select indices  index tolist   Out 797     b    d    e

[python] Python Pandas: Get index of rows which column matches certain value

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