It's not possible. A byte is 0 to 255. An int is a whole lot bigger than that. So, you can convert an int to a stream of bytes, but not to a byte.
We can convert numbers to strings using the str() method. We'll pass either a number or a variable into the parentheses of the method and then that numeric value will be converted into a string value.
To convert int to binary in Python, use the bin() method. The bin() is a built-in Python method that converts a decimal to a binary data type. The bin() function accepts a number as an argument and returns its equivalent binary string prefixed with “0b”.
From python 3.2 you can do
>>> (1024).to_bytes(2, byteorder='big')
b'\x04\x00'
https://docs.python.org/3/library/stdtypes.html#int.to_bytes
def int_to_bytes(x: int) -> bytes:
return x.to_bytes((x.bit_length() + 7) // 8, 'big')
def int_from_bytes(xbytes: bytes) -> int:
return int.from_bytes(xbytes, 'big')
Accordingly, x == int_from_bytes(int_to_bytes(x))
.
Note that the above encoding works only for unsigned (non-negative) integers.
For signed integers, the bit length is a bit more tricky to calculate:
def int_to_bytes(number: int) -> bytes:
return number.to_bytes(length=(8 + (number + (number < 0)).bit_length()) // 8, byteorder='big', signed=True)
def int_from_bytes(binary_data: bytes) -> Optional[int]:
return int.from_bytes(binary_data, byteorder='big', signed=True)
That's the way it was designed - and it makes sense because usually, you would call bytes
on an iterable instead of a single integer:
>>> bytes([3])
b'\x03'
The docs state this, as well as the docstring for bytes
:
>>> help(bytes)
...
bytes(int) -> bytes object of size given by the parameter initialized with null bytes
You can use the struct's pack:
In [11]: struct.pack(">I", 1)
Out[11]: '\x00\x00\x00\x01'
The ">" is the byte-order (big-endian) and the "I" is the format character. So you can be specific if you want to do something else:
In [12]: struct.pack("<H", 1)
Out[12]: '\x01\x00'
In [13]: struct.pack("B", 1)
Out[13]: '\x01'
This works the same on both python 2 and python 3.
Note: the inverse operation (bytes to int) can be done with unpack.
Python 3.5+ introduces %-interpolation (printf
-style formatting) for bytes:
>>> b'%d\r\n' % 3
b'3\r\n'
See PEP 0461 -- Adding % formatting to bytes and bytearray.
On earlier versions, you could use str
and .encode('ascii')
the result:
>>> s = '%d\r\n' % 3
>>> s.encode('ascii')
b'3\r\n'
Note: It is different from what int.to_bytes
produces:
>>> n = 3
>>> n.to_bytes((n.bit_length() + 7) // 8, 'big') or b'\0'
b'\x03'
>>> b'3' == b'\x33' != '\x03'
True
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