Pandas DataFrame.rmul

The DataFrame.rmul method in pandas performs element-wise multiplication of another value (or DataFrame/Series) with the calling DataFrame, with reverse operation priority. This is useful when you need to reverse the order of multiplication, such as when the scalar or other operand is on the left-hand side.

Syntax

The syntax for DataFrame.rmul is:

DataFrame.rmul(other, axis='columns', level=None, fill_value=None)

Here, DataFrame refers to the pandas DataFrame on which the method is called.

Parameters

Parameter	Description
`other`	The value, Series, or DataFrame to be multiplied with the calling DataFrame.
`axis`	Axis to broadcast over. Can be `'index'` (0) or `'columns'` (1). Defaults to `'columns'`.
`level`	If the axis is a MultiIndex, this parameter specifies the level to match for alignment. Defaults to `None`.
`fill_value`	Value to fill in for missing data on either side during the operation. Defaults to `None`.

Returns

A DataFrame with the reverse element-wise multiplication applied.

Examples

Basic Reverse Multiplication with a Scalar

Use rmul to perform reverse multiplication with a scalar.

Python Program

import pandas as pd

# Create a DataFrame
data = {
    'A': [1, 2, 3],
    'B': [4, 5, 6]
}
df = pd.DataFrame(data)

# Reverse multiply with a scalar
print("Reverse multiplication with scalar 10:")
result = 10 * df
print(result)

Output

Reverse multiplication with scalar 10:
    A   B
0  10  40
1  20  50
2  30  60

Reverse Multiplication with Another DataFrame

Use rmul to reverse multiply with another DataFrame of the same shape.

Python Program

import pandas as pd

# Create two DataFrames
data1 = {
    'A': [1, 2, 3],
    'B': [4, 5, 6]
}
data2 = {
    'A': [10, 20, 30],
    'B': [40, 50, 60]
}
df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

# Reverse multiply
print("Reverse multiplication with another DataFrame:")
result = df2.rmul(df1)
print(result)

Output

Reverse multiplication with another DataFrame:
     A     B
0   10   160
1   40   250
2   90   360

Reverse Multiplication with a Series

Use rmul to reverse multiply with a Series along a specified axis.

Python Program

import pandas as pd

# Create a DataFrame and a Series
data = {
    'A': [1, 2, 3],
    'B': [4, 5, 6]
}
df = pd.DataFrame(data)
series = pd.Series([10, 20, 30])

# Reverse multiply along index axis
print("Reverse multiplication with a Series along index:")
result = series.rmul(df, axis=0)
print(result)

Output

Reverse multiplication with a Series along index:
     A    B
0   10   40
1   40  100
2   90  180

Using `fill_value` for Missing Data

Use the fill_value parameter to specify a value for filling missing data during the operation.

Python Program

import pandas as pd

# Create two DataFrames with missing values
data1 = {
    'A': [1, 2, None],
    'B': [4, None, 6]
}
data2 = {
    'A': [10, 20, 30],
    'B': [40, 50, None]
}
df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

# Reverse multiply with fill_value
print("Reverse multiplication with fill_value=1:")
result = df2.rmul(df1, fill_value=1)
print(result)

Output

Reverse multiplication with fill_value=1:
      A      B
0   10.0   160.0
1   40.0    50.0
2   30.0     6.0

Summary

In this tutorial, we explored the DataFrame.rmul method in pandas. Key takeaways include:

Using rmul for reverse element-wise multiplication with scalars, Series, or DataFrames.
Specifying an axis for alignment during the operation.
Handling missing data with the fill_value parameter.

The DataFrame.rmul method is a versatile tool for reverse multiplication in pandas.