Editing Python programming (section)

== Converting binary string and text string ==

The [https://docs.python.org/3/library/binascii.html binascii] module contains a number of methods to convert between binary and various ASCII-encoded binary representations.

<pre>>>> import binascii

>>> b = binascii.hexlify(b'binary_string') < -- convert from binary string to binary hexadecimal representation...similar to bytes.hex() except this returns binary string
							  
>>> b
							  
b'62696e6172795f737472696e67' < -- binary hexadecimal representation
>>> binascii.a2b_hex(b) <-- convert from binary hexadecimal to binary string
							  
b'binary_string'

>>> bytes.hex(b) < -- convert binary hexadecimal b'62696e6172795f737472696e67' to octet strings (takes up twice as much space)
							  
'3632363936653631373237393566373337343732363936653637'

>>> s = '1234567890'  < -- create sample string
							  
>>> bo = bytes(s, 'ascii') < -- create bytes object of string (binary string)
							  
>>> bo
							  
b'1234567890' < -- notice the little b in front of the first single quote
>>> octet_string = bytes.hex(bo)  < -- convert bytes object (binary string) to octet string
							  
>>> octet_string
							  
'31323334353637383930'</pre>

=== Converting back and forth with binascii, bytes, ASCII symbols, and ASCII as hexadecimal ===

<pre>>>> import datetime

>>> dt = datetime.datetime.utcnow()

>>> dt
datetime.datetime(2019, 4, 2, 1, 36, 8, 931977)

>>> f = '{:%Y%m%d%H%M%S.%f}'

>>> f.format(dt)
'20190402013608.931977'

>>> f.format(dt)[:-3]+'Z'
'20190402013608.931Z'

>>> t = f.format(dt)[:-3]+'Z'

>>> t
'20190402013608.931Z'

>>> bytes(t,'ascii')
b'20190402013608.931Z'

>>> import binascii

>>> binascii.hexlify(bytes(t,'ascii'))
b'32303139303430323031333630382e3933315a'

>>> binascii.hexlify(bytes(t,'ascii'))
b'32303139303430323031333630382e3933315a'

>>> bt = binascii.hexlify(bytes(t,'ascii'))

>>> bt
b'32303139303430323031333630382e3933315a'

>>> bt.decode()
'32303139303430323031333630382e3933315a'

>>> '32303139303430323031333630382e3933315a'.encode()
b'32303139303430323031333630382e3933315a'

>>> b'32303139303430323031333630382e3933315a'.decode()
'32303139303430323031333630382e3933315a'

>>> binascii.unhexlify(bt)  < -- change from binary ASCII encoded as hexadecimals to binary string of ASCII symbols	
b'20190402013608.931Z'

>>> binascii.unhexlify(bt).decode()  < -- do the same as above but also change from binary string to text string
	
'20190402013608.931Z'

>>> st = bt.decode()  < -- convert binary string to text string

>>> st
'32303139303430323031333630382e3933315a'

>>> bytearray.fromhex(st).decode() < -- change from text string ASCII encoded as hexadecimals to text string of ASCII symbols
'20190402013608.931Z'</pre>