Conditional Logic on Pandas DataFrame

Question

How to apply conditional logic to a Pandas DataFrame    See DataFrame shown below      data desired output 0     1          False 1     2          False 2     3           True 3     4           True   My original data is show in the  data  column and the desired output is shown next to it  If the number in  data  is below 2 5  the desired output is False   I could apply a loop and do re-construct the DataFrame    but that would be  un-pythonic

User · Answer

In  34   import pandas as pd  In  35   import numpy as np  In  36    df   pd DataFrame  1 2 3 4   columns   data     In  37   df Out 37       data 0     1 1     2 2     3 3     4  In  38   df  desired output     np where df  data    lt 2 5   False    True    In  39   df Out 39       data desired output 0     1          False 1     2          False 2     3           True 3     4           True

User · Answer

In this specific example  where the DataFrame is only one column  you can write this elegantly as   df  desired output     df le 2 5    le tests whether elements are less than or equal 2 5  similarly lt for less than  gt and ge

User · Answer

In  1   df Out 1      data 0     1 1     2 2     3 3     4   You want to apply a function that conditionally returns a value based on the selected dataframe column     In  2   df  data   apply lambda x   true  if x  lt   2 5 else  false   Out 2   0     true 1     true 2    false 3    false Name  data   You can then assign that returned column to a new column in your dataframe   In  3   df  desired output     df  data   apply lambda x   true  if x  lt   2 5 else  false    In  4   df Out 4      data desired output 0     1           true 1     2           true 2     3          false 3     4          false

User · Answer

Just compare the column with that value   In  9   df   pandas DataFrame  1 2 3 4   columns   data     In  10   df Out 10       data 0     1 1     2 2     3 3     4  In  11   df  desired     df  data    gt  2 5 In  11   df Out 12       data desired 0     1   False 1     2   False 2     3    True 3     4    True

[python] Conditional Logic on Pandas DataFrame

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