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Pandas DataFrame.where()

Pandas DataFrame.where() with What is Python Pandas, Reading Multiple Files, Null values, Multiple index, Application, Application Basics, Resampling, Plotting the data, Moving windows functions, Series, Read the file, Data operations, Filter Data etc.

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Pandas DataFrame.where()

The main task of the where() method is to check the data frame for one or more conditions and return the result accordingly. By default, if the rows are not satisfying the condition, it is filled with NaN value.

Syntax

DataFrame.where(cond, other=nan, inplace=False, axis=None, level=None, errors='raise', try_cast=False, raise_on_error=None)

Parameters

  • cond: It refers to one or more conditions to check the data frame.
  • other: It replaces the rows that do not satisfy the condition with the user-defined object; the default value is NaN.
  • inplace: Returns the boolean value. If the value is true, it makes the changes in the dataframe itself.
  • axis: An axis to check( row or columns).

Returns

Example1

import pandas as pd
import numpy as np
a = pd.Series(range(5))
a.where(a > 0)
a.mask(a > 0) 
a.where(a > 1, 10)
info = pd.DataFrame(np.arange(10).reshape(-1, 2), columns=['A', 'B'])
info
b = info % 3 == 0
info.where(b, -info)
info.where(b, -info) == np.where(b, info, -info)
info.where(b, -info) == info.mask(~b, -info)

Output

     A        B
0   True     True
1   True     True
2   True     True
3   True     True
4   True     True
Next TopicAdd column to DataFrame columns




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