>>> s = "Hello World" >>> b = bytearray(s) >>> b bytearray(b'Hello World') >>> b[:5] = "Cruel" >>> b bytearray(b'Cruel World') >>> for i in b: ... print i ... 67 114 117 101 108 32 87 111 114 108 100 >>> b.append(33) >>> b bytearray(b'Cruel World!') >>> print b Cruel World! |
The usage
b"mystring" was new to me as well. According to this SO answer:the b prefix for string literals is ineffective in 2.6, but it is a useful marker in the program, which flags explicitly the intent of the programmer to have the string as a data string rather than a text string. This info can then be used by the 2to3 converter or similar utilities when the program is ported to Py3k.More info here (thanks, Ned).
A bytearray has the methods of lists including
__getitem__ and __setitem__. Unusually for Python, one can use arguments of both int and str types. The actual type of a bytearray item is < type 'int'>.>>> b = bytearray('Hello World!')
>>> b[-1] = '*'
>>> b
bytearray(b'Hello World*')
>>> ord('!')
33
>>> b[-1] = 33
>>> b
bytearray(b'Hello World!') |
We can use a bytearray to do a small job of encryption in a very convenient way:
>>> import numpy as np
>>> msg = bytearray("Hello World")
>>> n = len(msg)
>>> L = np.random.randint(0,256,n)
>>> key = bytearray(list(L))
>>> len(key)
11
>>> key
bytearray(b'N\x963\x8a\x06\xf2\xe9\x92\xb9\xf4L')
>>>
>>>
>>> ctext = bytearray()
>>> for c,k in zip(msg,key):
... ctext.append(c ^ k)
...
>>> ctext
bytearray(b'\x06\xf3_\xe6i\xd2\xbe\xfd\xcb\x98(')
>>> ptext = bytearray()
>>> for c,k in zip(ctext,key):
... ptext.append(c ^ k)
...
>>> ptext
bytearray(b'Hello World')
|
