Python in a Nutshell, 2nd Edition

The array Module

The array module supplies a type, also called array, whose instances are mutable sequences, like lists. An array a is a one-dimensional sequence whose items can be only characters, or only numbers of one specific numeric type, fixed when you create a.

array.array’s main advantage is that, compared to a list, it can save memory to hold objects all of the same (numeric or character) type. An array object a has a one-character, read-only attribute a.typecode, which is set on creation and gives the type of a’s items. Table 16-1 shows the possible typecodes for array.

Table 16-1. Typecodes for the array module

Typecode	C type	Python type	Minimum size
'c'	char	str (length 1)	1 byte
'b'	char	int	1 byte
'B'	unsigned char	int	1 byte
'U'	unicode char	unicode (lenth 1)	2 bytes
'h'	short	int	2 bytes
'H'	unsigned short	int	2 bytes
'i'	int	int	2 bytes
'I'	unsigned	long	2 bytes
'l'	long	int	4 bytes
'L'	unsigned long	long	4 bytes
'f'	float	float	4 bytes
'd'	double	float	8 bytes

The size in bytes of each item may be larger than the minimum, depending on the machine’s architecture, and is available as the read-only attribute a.itemsize. Module array supplies just the type object called array.

array

array(typecode,init='') Creates and returns an array object a with the given typecode. init can be a plain string whose length is a multiple of itemsize; the string’s bytes, interpreted as machine values, directly initialize a’s items. Alternatively, init can be any iterable (of characters when typecode is 'c', otherwise of numbers): each item ...