Python Pandas iterate over rows and access column names

Question

I am trying to iterate over the rows of a Python Pandas dataframe  Within each row of the dataframe  I am trying to to refer to each value along a row by its column name    Here is what I have   import numpy as np import pandas as pd  df   pd DataFrame np random rand 10 4  columns list  ABCD    print df           A         B         C         D 0  0 351741  0 186022  0 238705  0 081457 1  0 950817  0 665594  0 671151  0 730102 2  0 727996  0 442725  0 658816  0 003515 3  0 155604  0 567044  0 943466  0 666576 4  0 056922  0 751562  0 135624  0 597252 5  0 577770  0 995546  0 984923  0 123392 6  0 121061  0 490894  0 134702  0 358296 7  0 895856  0 617628  0 722529  0 794110 8  0 611006  0 328815  0 395859  0 507364 9  0 616169  0 527488  0 186614  0 278792   I used this approach to iterate  but it is only giving me part of the solution - after selecting a row in each iteration  how do I access row elements by their column name   Here is what I am trying to do   for row in df iterrows        print row loc 0  A       print row A     print row index     My understanding is that the row is a Pandas series  But I have no way to index into the Series   Is it possible to use column names while simultaneously iterating over rows

User · Answer

for i in range 1 len na rm columns               print   column name    na rm columns i     Output    column name  seretide price column name  symbicort mkt shr column name  symbicort price

User · Answer

The item from iterrows   is not a Series  but a tuple of  index  Series   so you can unpack the tuple in the for loop like so   for  idx  row  in df iterrows        print row loc  A        print row A      print row index    0 890618586836  0 890618586836  Index   A    B    C    D    dtype  object

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This was not as straightforward as I would have hoped  You need to use enumerate to keep track of how many columns you have  Then use that counter to look up the name of the column  The accepted answer does not show you how to access the column names dynamically  for row in df itertuples index False  name None       for k v in enumerate row           print  quot column   0  quot  format df columns values k            print  quot value   0  quot  format v

User · Answer

How to iterate efficiently  If you really have to iterate a Pandas dataframe  you will probably want to avoid using iterrows    There are different methods and the usual iterrows   is far from being the best  itertuples   can be 100 times faster   In short    As a general rule  use df itertuples name None   In particular  when you have a fixed number columns and less than 255 columns  See point  3  Otherwise  use df itertuples   except if your columns have special characters such as spaces or  -   See point  2  It is possible to use itertuples   even if your dataframe has strange columns by using the last example  See point  4  Only use iterrows   if you cannot the previous solutions  See point  1    Different methods to iterate over rows in a Pandas dataframe   Generate a random dataframe with a million rows and 4 columns       df   pd DataFrame np random randint 0  100  size  1000000  4    columns list  ABCD        print df    1  The usual iterrows   is convenient  but damn slow   start time   time clock   result   0 for    row in df iterrows        result    max row  B    row  C     total elapsed time   round time clock   - start time  2  print  1  Iterrows done in    seconds  result       format total elapsed time  result     2  The default itertuples   is already much faster  but it doesn t work with column names such as My Col-Name is very Strange  you should avoid this method if your columns are repeated or if a column name cannot be simply converted to a Python variable name     start time   time clock   result   0 for row in df itertuples index False       result    max row B  row C   total elapsed time   round time clock   - start time  2  print  2  Named Itertuples done in    seconds  result       format total elapsed time  result     3  The default itertuples   using name None is even faster but not really convenient as you have to define a variable per column   start time   time clock   result   0 for    col1  col2  col3  col4  in df itertuples name None       result    max col2  col3   total elapsed time   round time clock   - start time  2  print  3  Itertuples done in    seconds  result       format total elapsed time  result     4  Finally  the named itertuples   is slower than the previous point  but you do not have to define a variable per column and it works with column names such as My Col-Name is very Strange   start time   time clock   result   0 for row in df itertuples index False       result    max row df columns get loc  B     row df columns get loc  C      total elapsed time   round time clock   - start time  2  print  4  Polyvalent Itertuples working even with special characters in the column name done in    seconds  result       format total elapsed time  result     Output            A   B   C   D 0       41  63  42  23 1       54   9  24  65 2       15  34  10   9 3       39  94  82  97 4        4  88  79  54                        999995  48  27   4  25 999996  16  51  34  28 999997   1  39  61  14 999998  66  51  27  70 999999  51  53  47  99   1000000 rows x 4 columns   1  Iterrows done in 104 96 seconds  result   66151519 2  Named Itertuples done in 1 26 seconds  result   66151519 3  Itertuples done in 0 94 seconds  result   66151519 4  Polyvalent Itertuples working even with special characters in the column name done in 2 94 seconds  result   66151519   This article is a very interesting comparison between iterrows and itertuples

User · Answer

I also like itertuples    for row in df itertuples        print row A      print row Index    since row is a named tuples  if you meant to access values on each row this should be MUCH faster  speed run    df   pd DataFrame  x for x in range 1000 1000    columns   A    st time time   for index  row in df iterrows        row A print time time  -st  45 05799984931946  st time time   for row in df itertuples        row A print time time   - st  0 48400020599365234

[python] Python Pandas iterate over rows and access column names

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