Convert NumPy Array to Pandas DataFrame

To convert a NumPy array to a Pandas DataFrame, you can use the pd.DataFrame constructor provided by the Pandas library. We can convert the Numpy array to Pandas DataFrame by using various syntaxes. In this article, I will explain how to convert a numpy array to Pandas DataFrame with examples.

Key Points –

Use pd.DataFrame(array) to convert a 2D NumPy array directly into a DataFrame.
Ensure correct data types by converting arrays using methods like astype() when necessary.
This method can be useful for converting structured or record arrays into a DataFrame.
Use transpose() to switch rows and columns before conversion if needed.
Consider how to handle NaN values in your array to maintain DataFrame integrity.
Converting large arrays may be resource-intensive; ensure efficient memory management.

Quick Examples to Convert NumPy Array to DataFrame

If you are in a hurry, below are some quick examples of how to convert the NumPy array to DataFrame.


# Quick examples to convert numpy array to dataframe

# Example 1: Convert 2-dimensional NumPy array
array = np.array([['Spark', 20000, 1000], ['PySpark', 25000, 2300], ['Python', 22000, 12000]])
df = pd.DataFrame({'Course': array[:, 0], 'Fee': array[:, 1], 'Discount': array[:, 2]})

# Example 2: Convert array to DataFrame 
# Using from_records()
array = np.arange(6).reshape(2, 3)
df = pd.DataFrame.from_records(array)

# Example 4: Convert array to DataFrame
arr1  = np.arange(start = 1, stop = 10, step = 1).reshape(-1)
arr2 = np.random.rand(9).reshape(-1)
df = pd.DataFrame()
df['col1'] = arr1
df['col2'] = arr2

# Example 5 : Convert using transpose() function
array = np.array([['Courses', 'Fee'], ['Spark', 'PySpark'], [20000, 25000]])
df = pd.DataFrame(i for i in array).transpose()
df.drop(0, axis=1, inplace=True)
df.columns = array[0]

What is Numpy Array?

We know that a NumPy array is a data structure (usually numbers) that holds values of the same type, similar to a list. But arrays are more efficient than Python lists and also much more compact. In case you want the data in an array you should able to convert Series to arrayor Pandas DataFrame to a Numpy array

Since our article is to convert NumPy Assay to DataFrame, Let's Create NumPy array using np.array() function and then convert it to DataFrame.


import numpy as np 

# Create a 2 dimensional numpy array
array = np.array([['Spark', 20000, 1000], ['PySpark', 25000, 2300], ['Python', 22000, 1200]])
print("Create numpy array:\n",array)
print(type(array))

Yields below output.

What is DataFrame?

Pandas DataFrame is a Two-Dimensional data structure, an immutable, heterogeneous tabular data structure with labeled axes rows, and columns. pandas Dataframe consists of three components principal, data, rows, and columns. Pandas is built on the NumPy library and written in languages like Python, Cython, and C.

Convert NumPy Array to Pandas DataFrame

Let's convert the above NumPy array to DataFrame using the below syntax. In this syntax, I am using NumPy slicing technique for providing column elements to DataFrame.


# Convert array to DataFrame
df = pd.DataFrame({'Course': array[:, 0], 'Fee': array[:, 1], 'Discount': array[:, 2]})
print(df)

Yields below output.

Convert Array to DataFrame using from_records()

In this example, I will create 2-D NumPy array using arange() and reshape() functions. I will use this array and convert to DataFrame using from_records() function.


# Create a numpy array
array = np.arange(6).reshape(2, 3)
print(array)
# Output:
# [[0 1 2]
# [3 4 5]]

Let's convert DataFrame from the array by using the from_records() function. In this syntax pass array into the from_records() function. For example,


# Convert array to DataFrame
df = pd.DataFrame.from_records(array)
print(df)

# Output:
#    0  1  2
# 0  0  1  2
# 1  3  4  5

Convert Multiple Arrays to DataFrame

If you have two NumPy array objects and wanted to convert them to DataFrame, assign each array as a column to Dataframe. Here, I am using arrange() and random.rand() functions to create array.


#  create an array 
arr1  = np.arange(start = 1, stop = 10, step = 1).reshape(-1)
arr2 = np.random.rand(9).reshape(-1)
print(arr1)
print(arr2)
print(arr1.shape)
print(arr2.shape)

Yields below output.


# Output:
[1 2 3 4 5 6 7 8 9]
[0.25903374 0.98651581 0.94674926 0.16608304 0.99794979 0.38816292
 0.50690008 0.03360956 0.37643328]
(9,)
(9,)

Let's convert the array to DataFrame, In order to create DataFrame, we can set the above arrays as a column of DataFrame which we want to convert from given arrays.


# Convert array to DataFrame
df = pd.DataFrame()
df['col1'] = arr1
df['col2'] = arr2
print(df.head())

Yields below output.


# Output:
  col1      col2
0     1  0.259034
1     2  0.986516
2     3  0.946749
3     4  0.166083
4     5  0.997950

Another Example to Convert

In this example, I will create NumPy array using numpy.array() and I will use this array to convert DataFrame.


# Create an array 
array = np.array([['Courses', 'Fee'], ['Spark', 'PySpark'], [20000, 25000]])
print(array)

# Output :
# [['Courses' 'Fee']
#  ['Spark' 'PySpark']
#  ['20000' '25000']]

Let's convert the above array to DataFrame using Python for loop and pd.transpose() function. For example,


# Convert array DataFrame
df = pd.DataFrame(i for i in array).transpose()
df.drop(0, axis=1, inplace=True)
df.columns = array[0]
print(df)

# Output:
#    Courses    Fee
# 0    Spark  20000
# 1  PySpark  25000

FAQ on Convert NumPy Array to Pandas DataFrame

Pandas DataFrames provide a tabular data structure with labeled axes (rows and columns). Converting a NumPy array to a Pandas DataFrame allows you to leverage the additional features and functionality provided by Pandas, such as labeled indexing, convenient data manipulation methods, and seamless integration with other data analysis tools.

You can convert a NumPy array to a Pandas DataFrame with custom column names and index labels using the pd.DataFrame constructor and providing the columns and index parameters.

Pandas DataFrames can handle mixed data types. When you convert a NumPy array to a DataFrame, Pandas will automatically infer the data types for each column. However, be aware that having mixed data types in a single column may result in the column being assigned the object data type, which may not be as efficient for numerical operations.

Converting large arrays to DataFrames involves creating a new data structure, and depending on the size of your data, it may have performance implications. When working with large datasets, it's advisable to consider memory usage and potential performance bottlenecks. Additionally, make sure to optimize your data types and use Pandas features efficiently to avoid unnecessary overhead.

You can use various indexing and slicing methods provided by Pandas to access specific elements or slices. For example, you can use loc and iloc for label-based and integer-based indexing, respectively.

Conclusion

In this article, I have explained how to convert a Numpy array to Pandas DataFrame using various syntaxes with examples.

Happy learning !!

Convert NumPy Array to Pandas DataFrame

Quick Examples to Convert NumPy Array to DataFrame

What is Numpy Array?

What is DataFrame?

Convert NumPy Array to Pandas DataFrame

Convert Array to DataFrame using from_records()

Convert Multiple Arrays to DataFrame

Another Example to Convert

FAQ on Convert NumPy Array to Pandas DataFrame

Conclusion

Related Articles