Python Array fromfile() Method

The fromfile() method in Python is used to read items from a file object and append them to an array. This method is useful for reading binary data directly from a file and converting it into an array of elements.

Table of Contents

1. Introduction
2. Importing the array Module
3. fromfile() Method Syntax
4. Understanding fromfile()
5. Examples
   • Basic Usage
   • Reading Data from a Binary File
6. Real-World Use Case
7. Conclusion

Introduction

The fromfile() method is a built-in method for array objects in Python, which are provided by the array module. This method allows you to append items from a file object, making it convenient for handling binary data.

Importing the array Module

Before using the fromfile() method, you need to import the array module, which provides the array object.

import array

fromfile() Method Syntax

The syntax for the fromfile() method is as follows:

array.fromfile(f, n)

Parameters:

• f: A file object from which elements are to be read.
• n: The number of elements to read from the file.

Returns:

• None. The method appends the elements read from the file to the array.

Understanding fromfile()

The fromfile() method reads a specified number of elements from the given file object and appends them to the array. The file must contain raw binary data corresponding to the type code of the array.

Examples

Basic Usage

To demonstrate the basic usage of fromfile(), we will create a binary file, write data to it, and then read the data back into an array.

Example

import array

# Creating an array of integers
arr = array.array('i')

# Writing binary data to a file
with open("data.bin", "wb") as file:
    file.write(array.array('i', [1, 2, 3, 4, 5]).tobytes())

# Reading data from the binary file into the array
with open("data.bin", "rb") as file:
    arr.fromfile(file, 5)

# Printing the array
print("Array after fromfile:", arr)

Output:

Array after fromfile: array('i', [1, 2, 3, 4, 5])

Reading Data from a Binary File

This example shows how to read data from a binary file and append it to an array using fromfile().

Example

import array

# Creating an array of floats
arr = array.array('f')

# Writing binary data to a file
with open("float_data.bin", "wb") as file:
    file.write(array.array('f', [1.1, 2.2, 3.3, 4.4, 5.5]).tobytes())

# Reading data from the binary file into the array
with open("float_data.bin", "rb") as file:
    arr.fromfile(file, 5)

# Printing the array
print("Array after fromfile:", arr)

Output:

Array after fromfile: array('f', [1.100000023841858, 2.200000047683716, 3.299999952316284, 4.400000095367432, 5.5])

Real-World Use Case

Reading Sensor Data from a Binary File

In real-world applications, the fromfile() method can be used to read binary data recorded by sensors and convert it into an array for analysis.

Example

import array

# Creating an array to store sensor data
sensor_data = array.array('d')  # 'd' is the type code for double (float)

# Simulating writing sensor data to a binary file
with open("sensor_data.bin", "wb") as file:
    file.write(array.array('d', [10.1, 20.2, 30.3, 40.4, 50.5]).tobytes())

# Reading sensor data from the binary file into the array
with open("sensor_data.bin", "rb") as file:
    sensor_data.fromfile(file, 5)

# Printing the sensor data array
print("Sensor data array:", sensor_data)

Output:

Sensor data array: array('d', [10.1, 20.2, 30.3, 40.4, 50.5])

Conclusion

The fromfile() method in Python is used to read elements from a binary file and append them to an array. This method is particularly useful for handling binary data from various sources.