How to convert a Pandas DataFrame to a NumPy array and back?

NumPy: Interoperability Exercise-13 with Solution

Write a NumPy program to create a Pandas DataFrame, convert it to a NumPy array, and then convert it back to a DataFrame.

Sample Solution:

Python Code:

import numpy as np
import pandas as pd

# Create a Pandas DataFrame
data = {
    'A': [1, 2, 3, 4],
    'B': [5, 6, 7, 8],
    'C': [9, 10, 11, 12]
}
df = pd.DataFrame(data)

# Print the original DataFrame
print("Original DataFrame:")
print(df)
print("Type:",type(df))


# Convert the DataFrame to a NumPy array
array = df.to_numpy()


# Print the NumPy array
print("\nNumPy Array:")
print(array)
print("Type:",type(array))


# Convert the NumPy array back to a DataFrame
df_back = pd.DataFrame(array, columns=df.columns)

# Print the DataFrame converted back from the NumPy array
print("\nDataFrame from NumPy Array:")
print(df_back)
print("Type:",type(df_back))

Output:

Original DataFrame:
   A  B   C
0  1  5   9
1  2  6  10
2  3  7  11
3  4  8  12
Type: <class 'pandas.core.frame.DataFrame'>

NumPy Array:
[[ 1  5  9]
 [ 2  6 10]
 [ 3  7 11]
 [ 4  8 12]]
Type: <class 'numpy.ndarray'>

DataFrame from NumPy Array:
   A  B   C
0  1  5   9
1  2  6  10
2  3  7  11
3  4  8  12
Type: <class 'pandas.core.frame.DataFrame'>

Explanation:

• Import NumPy and Pandas Libraries: Import the NumPy and Pandas libraries to work with arrays and DataFrames.
• Create Pandas DataFrame: Define a Pandas DataFrame with some example data.
• Convert DataFrame to NumPy Array: Use the to_numpy() method of the DataFrame to convert it into a NumPy array.
• Convert NumPy Array Back to DataFrame: Use the pd.DataFrame() constructor to convert the NumPy array back into a DataFrame, ensuring the column names match the original DataFrame.
• Print Original DataFrame: Output the original DataFrame to compare with the converted versions.
• Print NumPy Array: Output the NumPy array to verify the conversion.
• Print DataFrame from NumPy Array: Output the DataFrame converted back from the NumPy array to verify the conversion accuracy.

Python-Numpy Code Editor:

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