How to use the DataFrame.combine() method in pandas
Overview
A Python library, pandas, is specially used for data manipulation and analysis. It provides multiple built-in methods for manipulating tables into DataFrames. In this shot, we are going to discuss the combine() method from the DataFrame module of this library.
The DataFrame.combine() method is used to combine a DataFrame with the other DataFrame by using func to get element-wise combined columns. The dimensions of the resulting DataFrame will be the union of these DataFrames.
Syntax
DataFrame.combine(other, func, fill_value=None, overwrite=True)
Parameters
It takes the following argument values.
other: Another DataFrame to combine element-wise.func: A function that takes two pandas series as inputs and returns a scaler series. It helps to combine two DataFrames.fill_value=None: The value to fill empty or NaNs before merging two columns. Its default value isNone.overwrite=True: If overwrite is set toTrue, columns inselfwill be overwritten with NaNs inother. Its default value isTrue.
Return value
The pandas DataFrame returns a combination of two self and other DataFrames.
Explanation
In this code snippet, we are going to elaborate on how the combine() method can be used in different scenarios.
# load pandas module in programimport pandas as pd# creating two DataFramesdf1 = pd.DataFrame({'A': [1,2,3], 'B': [0,-1,4]})df2 = pd.DataFrame({'A': [0,2,1], 'B': [-3,4,9]})smaller = lambda s1, s2: s1 if s1.sum() < s2.sum() else s2df1.combine(df2, func=smaller)print(df1)# creating another two dataframes to check the functionality of fill_valuedf3 = pd.DataFrame({'A': [0, 0], 'B': [None, 4]})df4 = pd.DataFrame({'A': [1, 1], 'B': [3, 3]})df1.combine(df4, smaller, fill_value=-5)print(df3)
Explanation
- Lines 1–5: We import the pandas library as
pdin the program. In lines 4 and 5, we create two data framesdf1anddf2. - Line 6: We define a
lambdafunction used to broadcast input values. It returnss1ifs1.sum() < s2.sum(). Otherwise, it returnss2. - Line 7: We invoke
pandas.combine()to merge two DataFrames, such asdf1&df2. - Lines 10 and 11: We create new DataFrames
df3anddf4. - Line 12: We then invoke
pandas.combine()to mergedf3anddf4. It's takingdf4,smaller, andfill_value=-5as arguments. In case of missing values, it will be replaced with-5.
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