Python doesn't have concept of array as in C/C++/Java etc. But it does

Python doesn't have concept of array as in C/C++/Java etc. But it does have array module in the standard library. How is it used?

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Array is a collection of more than one element of similar data type in C/C++/Java etc. Python doesn't have any built-in equivalent of array. Its List/tuple data types are COLLECTIONS, but items in it may be of different types.

Python's array module emulates C type array. The module defines 'array' class whose constructor requires two arguments:

array(typecode, initializer)

The typecode determines the type of array. Initializer should be a sequence with all elements of matching type.

Type code	C Type	Python Type
'b'	signed char	int
'B'	unsigned char	int
'u'	Py_UNICODE	Unicode character
'h'	signed short	int
'H'	unsigned short	int
'i'	signed int	int
'I'	unsigned int	int
'I'	signed long	int
'L'	unsigned long	int
'q'	signed long long	int
'Q'	unsigned long long	int
'f'	Float	float
'd'	Double	float

The array module defines typecodes attribute which RETURNS a STRING. Each character in the string represents a type code.

>>> array.typecodes 'bBuhHiIlLqQfd'

Following statement creates an integer array object:

>>> import array >>> arr=array.array('i', range(5)) >>> arr array('i', [0, 1, 2, 3, 4]) >>> type(arr) <class 'array.array'>

The initializer may be a byte like object. Following example builds an array from byte representation of string.

>>> arr=array.array('b', b'Hello') >>> arr array('b', [72, 101, 108, 108, 111])

Some of the useful methods of the array class are as follows:

extend():

This method appends items from list/tuple to the end of the array. Data type of array and iterable list/tuple must MATCH; if not, TypeError will be raised.

>>> arr=array.array('i', [0, 1, 2, 3, 4]) >>> arr1=array.array('i',[10,20,30]) >>> arr.extend(arr1) >>> arr array('i', [0, 1, 2, 3, 4, 10, 20, 30])

fromfile():

This method reads data from the file object and appends to an array.

>>> a=array.array('i') >>> file=open('test.txt','rb') >>> a.fromfile(file,file.tell()) >>> a array('i', [1819043144, 2035294319, 1852794996])

tofile():

This method write all items to the file object which must have write mode enabled.

>>> a=array.array('i', [10, 20, 30, 40, 50]) >>> file=open("temp.txt","WB") >>> a.tofile(file) >>> file.close() >>> file=open("temp.txt","rb") >>> file.read() b'\n\x00\x00\x00\x14\x00\x00\x00\x1e\x00\x00\x00(\x00\x00\x002\x00\x00\x00'

append():

This method appends a new item to the end of the array

fromlist():

This method appends items from the list to array. This is equivalent to for x in list: a.append(x)

>>> a=array.array('i') >>> a.append(10) >>> a array('i', [10]) >>> num=[20,30,40,50] >>> a.fromlist(num) >>> a array('i', [10, 20, 30, 40, 50])

insert():

Insert a new item in the array before specified position

>>> a=array.array('i', [10, 20, 30, 40, 50]) >>> a.insert(2,25) >>> a array('i', [10, 20, 25, 30, 40, 50])

pop():

This method returns item at given index after removing it from the array.

>>> a=array.array('i', [10, 20, 30, 40, 50]) >>> x=a.pop(2) >>> x 30 >>> a array('i', [10, 20, 40, 50])

remove():

This method removes first occurrence of given item from the array.

>>> a=array.array('i', [10, 20, 30, 40, 50]) >>> a.remove(30) >>> a array('i', [10, 20, 40, 50])

Python doesn't have concept of array as in C/C++/Java etc. But it does have array module in the standard library. How is it used?

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