Convert a NumPy array into a CSV file
Last Updated : 02 Feb, 2024
After completing your data science or data analysis project, you might want to save the data or share it with others. Exporting a NumPy array to a CSV file is the most common way of sharing data.
CSV file format is the easiest and most useful format for storing data and is convenient to share with others. So in this tutorial, we will see different methods to convert a NumPy array into a CSV file.
Different methods to convert a NumPy array to a CSV file are:
- Using DataFrame.to_csv() method
- Using NumPy_array.tofile() method
- Using NumPy.savetxt() method
- Using File Handling operations
Let's understand these methods better with examples.
Convert a NumPy array into a CSV using Dataframe.to_csv()
The DataFrame.to_csv() method is used to write a Dataframe into a CSV file.
To use DataFrame.to_csv() we have to first convert the NumPy array into pandas DataFrame and then save it to CSV format.
Example
Python3 import pandas as pd import numpy as np # create a dummy array arr = np.arange(1,11).reshape(2,5) print(arr) # convert array into dataframe DF = pd.DataFrame(arr) # save the dataframe as a csv file DF.to_csv("data1.csv") Output:
Convert a NumPy array into a CSV using numpy_array.tofile()
This method is used to write a NumPy array into the file.
The tofile() method allows us to save the NumPy array to a CSV file by calling the function with the NumPy array object and passing the CSV file_name and separator to the function.
Example
Python3 import numpy as np arr = np.arange(1,11) print(arr) # use the tofile() method # and use ',' as a separator arr.tofile('data2.csv', sep = ',') Output:
Convert a NumPy array into a CSV using numpy.savetxt()
The numpy.savetxt() method is used to save a NumPy array to a text file.
We can save the NumPy array to a CSV file by passing the file name, NumPy array, and the delimiter in the function numpy.savetxt().
Python3 # import numpy library import numpy # create an array a = numpy.array([[1, 6, 4], [2, 4, 8], [3, 9, 1]]) # save array into csv file numpy.savetxt("data3.csv", a, delimiter = ",") Output:
Convert a NumPy array into a CSV using file handling
File handling operations might be the easiest way to convert a NumPy array to a CSV file.
In Python, the str.format function is used to format strings. It inserts one or more replacement fields and placeholders, denoted by a pair of curly braces {}, into a string. The values supplied to the format function are inserted into these placeholders, resulting in a new string that includes the original input string and the formatted values.
The with keyword in Python is used in file handling operations. It ensures that the file is properly closed after it is no longer needed. This is particularly useful when writing to a CSV file, as it helps to prevent data corruption or loss. Here’s an example:
Example
Python3 # import numpy library import numpy # create an array a = numpy.array([[1, 6, 4], [2, 4, 8], [3, 9, 1], [11, 23, 43]]) # save array into csv file rows = ["{},{},{}".format(i, j, k) for i, j, k in a] text = "\n".join(rows) with open('data3.csv', 'w') as f: f.write(text) Output:
Also Read: How to Read CSV Files with NumPy?
Conclusion
Exporting the NumPy array into a CSV file is often required to save or share your data. Python offers many ways to save NumPy arrays into a CSV file. We have discussed four methods to convert a NumPy array into a CSV file.
In this tutorial, we have explained 4 easy methods to convert a NumPy array into a CSV file with examples and explanations. You can use any method you feel comfortable with.
Similar Reads
How to convert a dictionary into a NumPy array? In this article, we will learn how to convert a Python Dictionary into a numpy array which is more efficient for numerical operations and provides powerful tools for matrix and array manipulationsKey Steps to Convert a Dictionary to a NumPy ArrayUse dict.items(): This returns key-value pairs from th
3 min read
Convert a NumPy array to an image Converting a NumPy array to an image is a simple way to turn numbers into pictures. A NumPy array holds pixel values, which are just numbers that represent colors. Images, like PNG or JPEG, store these pixel values in a format we can see. In this process, the NumPy array turns into an image, with ea
3 min read
Convert 2D float array to 2D int array in NumPy Converting a 2D float array to a 2D integer array in NumPy is a straightforward process using the astype() method. This conversion can be useful in various data analysis and scientific computing tasks where integer data types are required or where memory efficiency is essential. In this article, we
8 min read
How to convert NumPy array to list ? This article will guide you through the process of convert a NumPy array to a list in Python, employing various methods and providing detailed examples for better understanding. Convert NumPy Array to List There are various ways to convert NumPy Array to List here we are discussing some generally us
4 min read
How to convert a list and tuple into NumPy arrays? In this article, let's discuss how to convert a list and tuple into arrays using NumPy. NumPy provides various methods to do the same using Python. Example: Input: [3, 4, 5, 6]Output: [3 4 5 6]Explanation: Python list is converted into NumPy ArrayInput: ([8, 4, 6], [1, 2, 3])Output: [[8 4 6] [1 2 3]
2 min read