Bytes in Python (5)

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*Memo:

• My post explains a bytes (1).
• My post explains a bytes (2).
• My post explains a bytes (3).
• My post explains a bytes (4).

bytes() can create a bytes with or without several types of values or can encode a string to a bytes as shown below:

*Memo to create a bytes:

• The 1st argument is source(Optional-Default:b''-Type:Bytes-like object/Iterable(int)/int):
  • int gives a null value(\x00) which represents no value.

*Memo to encode a string to a bytes:

• The 1st argument is source(Required-Type:str).
• The 2nd argument is encoding(Required-Type:str):
  • 'utf-8', 'utf-7', 'utf-16', 'big5', 'ascii', etc can be set to it.
  • You can see Standard Encodings for more possible values.
• The 3rd argument is errors(Optional-Default:'strict'-Type:str):
  • It controls encoding error with the error handlers, 'strict', 'ignore', 'replace', 'xmlcharrefreplace', 'backslashreplace', etc.
  • 'strict' raises UnicodeError if the character and byte, which cannot be encoded and decoded, exists respectively.
  • 'ignore' ignores the character and byte which cannot be encoded and decoded respectively.
  • 'replace' replaces the character and byte, which cannot be encoded and decoded, with ? for encoding and � for decoding respectively.
  • 'xmlcharrefreplace' replaces the character, which cannot be encoded, with the XML/HTML numeric character reference format &#num;:
    • It doesn't support decoding so error occurs for the byte which cannot be decoded while error doesn't occur for the byte which can be decoded.
  • 'backslashreplace' replaces the character and byte, which cannot be encoded and decoded, with the hexadecimal format \xhh, \uxxxx or \Uxxxxxxxx for encoding and \xhh for decoding respectively.
  • You can see more error handlers.
  • You can create your own error handler with codecs.register_error().

<Create a bytes>:

v = bytes()                            # Empty bytes
v = bytes(b'')                         # Empty bytes
v = bytes(source=b'12')                # bytes
v = bytes(source=bytearray(b'12'))     # bytearray
v = bytes(source=12)                   # int
v = bytes(source=True)                 # bool
v = bytes(source=[1, 2, 3])            # list(int)
v = bytes(source=(1, 2, 3))            # tuple(int)
v = bytes(source={1, 2, 3})            # set(int)
v = bytes(source=frozenset({1, 2, 3})) # frozenset(int)
v = bytes(source={1:2, 3:4})           # dict(int:int)
v = bytes(source={1:2, 3:4}.keys())    # dict(int:int).keys()
v = bytes(source={1:2, 3:4}.values())  # dict(int:int).values() 
v = bytes(source=iter([1, 2, 3]))      # iterator(int)
v = bytes(source=range(10, 20))        # range
# No error

print(type(bytes()))
# <class 'bytes'>

v = bytes(source='12')               # str
v = bytes(source=1.2)                # float
v = bytes(source=1.2+3.4j)           # complex
v = bytes(source={1:2, 3:4}.items()) # dict(int:int).items()
v = bytes(source=lambda: 10)         # function
# Error

# Empty bytes
v = bytes()
v = bytes(b'')

print(v)
# b''

v = bytes(source=b'12')            # bytes
v = bytes(source=bytearray(b'12')) # bytearray

print(v, v[0], v[1])
# b'12' 49 50

v = bytes(source=12) # int

print(v, v[0], v[1])
# b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' 0 0

v = bytes(source=[1, 2, 3]) # list
v = bytes(source=(1, 2, 3)) # tuple

print(v, v[0], v[1], v[2])
# b'\x01\x02\x03' 1 2 3

v = bytes(source={1, 2, 3})            # set
v = bytes(source=frozenset({1, 2, 3})) # frozenset(int)

print(v, v[0], v[1], v[2])
# b'\x01\x02\x03' 1 2 3

v = bytes(source={1:2, 3:4})        # dict(int:int)
v = bytes(source={1:2, 3:4}.keys()) # dict(int:int).keys()

print(v, v[0], v[1])
# b'\x01\x03' 1 3

v = bytes(source={1:2, 3:4}.values()) # dict(int:int).values() 

print(v, v[0], v[1])
# b'\x02\x04' 2 4

v = bytes(source=iter([1, 2, 3])) # iterator

print(v, v[0], v[1], v[2])
# b'\x01\x02\x03' 1 2 3

v = bytes(source=range(1, 4)) # range

print(v, v[0], v[1], v[2])
# b'\x01\x02\x03' 1 2 3

<Encode a string to an immutable byte string(bytes)>:

v = "Lёт's gφ!" # Let's go!

print(bytes(source=v, encoding='utf-8'))
print(bytes(source=v, encoding='utf-8', errors='strict'))
# b"L\xd1\x91\xd1\x82's g\xcf\x86!"

v = "Lёт's gφ!" # Let's go!

print(bytes(source=v, encoding='utf-7'))
# b"L+BFEEQg's g+A8Y!"

v = "Lёт's gφ!" # Let's go!

print(bytes(source=v, encoding='utf-16'))
# b"\xff\xfeL\x00Q\x04B\x04'\x00s\x00 \x00g\x00\xc6\x03!\x00"

v = "Lёт's gφ!" # Let's go!

print(bytes(source=v, encoding='big5'))
# b"L\xc7\xce\xc7\xdb's g\xa3p!"

import codecs

def hashreplace_handler(x):
    return ((x.end - x.start) * '#', x.end)

codecs.register_error('hashreplace', hashreplace_handler)

v = "Lёт's gφ!" # Let's go!

print(bytes(source=v, encoding='ascii', errors='ignore'))
# b"L's g!"

print(bytes(source=v, encoding='ascii', errors='replace'))
# b"L??'s g?!"

print(bytes(source=v, encoding='ascii', errors='xmlcharrefreplace'))
# b"Lёт's gφ!"

print(bytes(source=v, encoding='ascii', errors='backslashreplace'))
# b"L\\u0451\\u0442's g\\u03c6!"

print(bytes(source=v, encoding='ascii', errors='hashreplace'))
# b"L##'s g#!"

print(bytes(source=v, encoding='ascii', errors='strict'))
# UnicodeEncodeError: 'ascii' codec can't encode characters
# in position 1-2: ordinal not in range(128)