Python Array fromfile() Method

The Python arrayfromfile() method is used to append items from a file object to an array.

Syntax

Following is the syntax of Python arrayfromfile() method −

array_name.fromfile(f,n)

Parameters

This method accepts following parameters −

• f : This is the file object from which items are to be appended to the array.
• n : This is the number of items from file that need to be appended to the array.

Return Value

This method does not return any value.

Example 1

Following is the basic example of Python arrayfromfile() method −

#import  array moduleimport array as arr#open file object for writingf = open('my_file.txt','wb')#write array of integers to file objectarr1=arr.array("i", [1, 2, 3, 4, 5, 6, 7, 8, 9])print("Array in the file :",arr1 )arr1.tofile(f)#close filef.close()#open file for readingf = open('my_file.txt','rb')#initialize array with integer typearray_one = arr.array("i")#initialize array with integer typearray_two = arr.array("i")#read 3 items from filearray_one.fromfile(f,3)print("Appended array1 :",array_one)#Moving the cursor to the first positionf.seek(0)#read 6 items from filearray_two.fromfile(f,6)print("Appended array2 :",array_two)#close filef.close()

Output

Following is the output of the above code −

Array in the file : array('i', [1, 2, 3, 4, 5, 6, 7, 8, 9])Appended array1 : array('i', [1, 2, 3])Appended array2 : array('i', [1, 2, 3, 4, 5, 6])

Example 2

Lets try to append an array ofunicode charater data type from a file to another array −

import array as arrarr2=arr.array('u',['a','b','c','d'])print("Array elements in the file :",arr2)f=open('fromfile2.txt','wb')arr2.tofile(f)f.close()arr3=arr.array('u')f1=open("fromfile2.txt","rb")arr3.fromfile(f1,len(arr2))print('Array element after appending from file :',arr3)f.close()

Output

Array elements in the file : array('u', 'abcd')Array element after appending from file : array('u', 'abcd')

Example 3

In this method, if number of items or elements of filef has less than then items we getEOF Error.

Here, number of file elements arefive andn value mentioned issix

import array as arrarr3=arr.array('d',[5.6,3.9,23.5,45.7,12.7])print("Length of the array in the file", len(arr3))print("Array elements in the file :",arr3)f=open('fromfile2.txt','wb')arr3.tofile(f)f.close()arr4=arr.array('d')f1=open("fromfile2.txt","rb")arr4.fromfile(f1,6)print('Array element after appending from file :',arr4)f.close()

Output

Length of the array in the file 5Array elements in the file : array('d', [5.6, 3.9, 23.5, 45.7, 12.7])Traceback (most recent call last):  File "E:\pgms\Arraymethods prgs\fromfile1.py", line 63, in    arr4.fromfile(f1,6)EOFError: read() didn't return enough bytes