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## Array - Sequence of Fixed-Type Data

# It's a list that's restricted to a single datatype

# which is setup when the array is created

# 'c' -> character

# 'f' -> float

# 'i' -> integer

# 'I' -> long

# 'u' -> unicode char

# more options at: http://docs.python.org/2/library/array.html

import array, binascii, tempfile, os

s = "This is the array."

a = array.array('c', s)

print 'As string:', s

print 'As array :', a

print 'As hex :', binascii.hexlify(a)

# most of the list functions work on arrays as well

a = array.array('i', xrange(4))

print 'Initial :', a

a.extend(xrange(3))

print 'Extended:', a

print 'Slice :', a[2:5]

print 'Iterator:'

print list(enumerate(a))

print

# write/read arrays to/from files

a = array.array('i', xrange(5))

print 'A1:', a

# write the array of numbers to a temporary file

output = tempfile.NamedTemporaryFile(delete=False)

a.tofile(output.file) # must be an actual file

output.flush()

#read the raw data

with open(output.name, 'rb') as input:

raw_data = input.read()

print 'Raw Contents:', binascii.hexlify(raw_data)

# read the data lines into an array

input.seek(0)

a2 = array.array('i')

a2.fromfile(input, len(a))

print 'A2:', a2

print

# Arrays make it easy to change the byte order (I'm big-endian due to being a network guy)

def to_hex(a):

chars_per_item = a.itemsize * 2 # 2 hex digits

hex_version = binascii.hexlify(a)

num_chunks = len(hex_version) / chars_per_item

for i in xrange(num_chunks):

start = i*chars_per_item

end = start + chars_per_item

yield hex_version[start:end]

a1 = array.array('i', xrange(5))

a2 = array.array('i', xrange(5))

a2.byteswap()

fmt = '%10s %10s %10s %10s'

print fmt % ('A1 hex', 'A1', 'A2 hex', 'A2')

print fmt % (('~' * 10,) * 4)

for values in zip(to_hex(a1), a1, to_hex(a2), a2):

print fmt % values