Byte data type python

Python Bytes, Bytearray

Python supports a range of types to store sequences. There are six sequence types: strings, byte sequences (bytes objects), byte arrays (bytearray objects), lists, tuples, and range objects.

Strings contain Unicode characters. Their literals are written in single or double quotes : ‘python’, «data». Bytes and bytearray objects contain single bytes – the former is immutable while the latter is a mutable sequence. Bytes objects can be constructed the constructor, bytes(), and from literals; use a b prefix with normal string syntax: b’python’. To construct byte arrays, use the bytearray() function.

• Bytes literals
• bytes() and bytearray() functions
• Create a bytes object in Python
• Convert bytes to string
• Convert hex string to bytes
• Numeric code representing a character of a bytes object in Python
• Define a mapping table characters for use with a bytes object in Python
• Convert bytes to hex in Python
• How to get the character from the numeric code in bytes objects in Python
• Determine the length of a bytes object in Python
• Use the operators + and * with bytes objects in Python
• How to get a byte from a bytes object in Python
• Create a bytearray object
• Difference between bytes and bytearray object in Python
• Convert a bytes to bytearray
• Slice of a bytes object in Python
• Difference between bytes and string object

Bytes literals

bytesliteral ::= bytesprefix(shortbytes | longbytes) bytesprefix ::= «b» | «B» | «br» | «Br» | «bR» | «BR» shortbytes ::= «‘» shortbytesitem* «‘» | ‘»‘ shortbytesitem* ‘»‘ longbytes ::= «»'» longbytesitem* «»'» | ‘»»»‘ longbytesitem* ‘»»»‘ shortbytesitem ::= shortbyteschar | bytesescapeseq longbytesitem ::= longbyteschar | bytesescapeseq shortbyteschar ::= longbyteschar ::= bytesescapeseq ::= «\»

bytes() and bytearray() functions

bytes([source[, encoding[, errors]]])

bytearray() function :

bytearray([source[, encoding[, errors]]])

The optional source parameter can be used to initialize the array in a few different ways:

• If it is a string, you must also give the encoding (and optionally, errors) parameters; bytearray() then converts the string to bytes using str.encode().
• If it is an integer, the array will have that size and will be initialized with null bytes.
• If it is an object conforming to the buffer interface, a read-only buffer of the object will be used to initialize the bytes array.
• If it is iterable, it must be an iterable of integers in the range 0

Without an argument, an array of size 0 is created.

Create a bytes object in Python

>>> x = b"Bytes objects are immutable sequences of single bytes" >>> print(x) b'Bytes objects are immutable sequences of single bytes' >>> 

#triple single or double quotes allows multiple lines x = b'''Python Tutorial, Javascript Tutorial, MySQL Tutorial''' print(x) 

b'Python Tutorial,\nJavascript Tutorial,\nMySQL Tutorial'

#created from a iterable of ints, string, bytes or buffer objects. x = bytes('Python, bytes', 'utf8') print(x) 

Convert bytes to string

#create a bytes object x = b'El ni\xc3\xb1o come camar\xc3\xb3n' print(x) 

b'El ni\xc3\xb1o come camar\xc3\xb3n'

# create a string using the decode() method of bytes. #This method takes an encoding argument, such as UTF-8, and optionally an errors argument. x = b'El ni\xc3\xb1o come camar\xc3\xb3n' s = x.decode() print(type(s)) print(s) 

#create a bytes object encoded using 'cp855' x = b'\xd8\xe1\xb7\xeb\xa8\xe5 \xd2\xb7\xe1' print(x) #return a string using decode 'cp855' y = x.decode('cp855') print(y) 

b'\xd8\xe1\xb7\xeb\xa8\xe5 \xd2\xb7\xe1' привет мир

Convert hex string to bytes

#create a string with hexadecimal data x = '45678c6c56f205876f72c64' print(x) 

#this class method returns a bytes object, decoding the given string object. #the string must contain two hexadecimal digits per byte. x = '45678c6c56f205876f72c64' y = bytes.fromhex(x) 

Numeric code representing a character of a bytes object in Python

#return an integer representing the Unicode code point of that character. x = ord(b'm') print(x) 

#create a bytes object y = b'Python bytes' #generates a list of codes from the characters of bytes z = list(y) print(z) 

[80, 121, 116, 104, 111, 110, 32, 98, 121, 116, 101, 115]

Define a mapping table characters for use with a bytes object in Python

#create a str x = b'Python mapping table characters' print(x) 

b'Python mapping table characters'

b_table = bytes.maketrans(b'abcdef', b'uvwxyz') print(type(b_table)) print(b_table) 

 
b'\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f !"#$%
&\'()*+,-./0123456789:;[email protected][\\]^_`uvwxyzghijklmnopqrstuvwxyz<|>~\x7f\x80\x81\x82\x83\x84\x85\x86\x87\x88\x89\x8a\x8b\x8c\x8d\x8e\x8f\x
90\x91\x92\x93\x94\x95\x96\x97\x98\x99\x9a\x9b\x9c\x9d\x9e\x9f\xa0\xa1\xa2\xa3\xa4\xa5\xa6\xa7\xa8\xa9\xaa\xab\xac\xad\xae\xaf\xb0\xb1\
xb2\xb3\xb4\xb5\xb6\xb7\xb8\xb9\xba\xbb\xbc\xbd\xbe\xbf\xc0\xc1\xc2\xc3\xc4\xc5\xc6\xc7\xc8\xc9\xca\xcb\xcc\xcd\xce\xcf\xd0\xd1\xd2\xd3
\xd4\xd5\xd6\xd7\xd8\xd9\xda\xdb\xdc\xdd\xde\xdf\xe0\xe1\xe2\xe3\xe4\xe5\xe6\xe7\xe8\xe9\xea\xeb\xec\xed\xee\xef\xf0\xf1\xf2\xf3\xf4\xf
5\xf6\xf7\xf8\xf9\xfa\xfb\xfc\xfd\xfe\xff'

b_table = bytes.maketrans(b'abcdef', b'uvwxyz') str = 'Write a Python function to find a distinct pair of numbers whose product is odd from a sequence of integer values.' b_new = str.translate(b_table) print(b_new) 

Writy u Python zunwtion to zinx u xistinwt puir oz numvyrs whosy proxuwt is oxx zrom u syquynwy oz intygyr vuluys.

Convert bytes to hex in Python

>>> import binascii >>> binascii.hexlify("Python".encode("utf8")) b'507974686f6e' >>> binascii.unhexlify(_).decode("utf8") 'Python' >>> 

How to get the character from the numeric code in bytes objects in Python

>>> #this method return a single character based on the integer value. >>> x = chr(60) >>> print(x) < >>> x = chr(50) >>> print(x) 2 >>> #create a list with integers in the range 0 through 255 >>> y = [70, 111, 106, 94, 101, 100, 22, 95, 105, 22, 91, 87, 125, 135] >>> print(y) [70, 111, 106, 94, 101, 100, 22, 95, 105, 22, 91, 87, 125, 135] >>> #create a bytes object from a list of integers in the range 0 through 255. >>> z = bytes(y) >>> print(z) b'Foj^ed\x16_i\x16[W>\x87' >>> 

Determine the length of a bytes object in Python

>>> #create a string >>> x = "Python, Bytes" >>> print(x) Python, Bytes >>> #know the length of the string using the len() function >>> print(len(x)) 13 >>> #create a bytes object >>> y = bytes(x, "utf8") >>> print(y) b'Python, Bytes' >>> #know the length of the bytes object using the len() function >>> print(len(y)) 13 >>> 

Use the operators + and * with bytes objects in Python

 >>> #create a bytes object >>> x = b"byte 213" >>> print(x) b'byte 213' >>> #The * operator allow repeat the characters of a bytes object >>> print(x * 5) b'byte 213byte 213byte 213byte 213byte 213' >>> #create two bytes objects. >>> x1 = bytes([70, 111, 106, 94, 101, 100, 22, 95, 105, 22, 91, 87, 125, 135]) >>> x2 = b"Python" >>> #The + operator allow create a new bytes object joining two or more bytes. >>> x = x1 + x2 >>> print(x) b'Foj^ed\x16_i\x16[W>\x87Python' >>> #create a bytes object combining operators >>> x = b"Python" + b"Bytes" * 3 + b"$" >>> print(x) b'PythonBytesBytesBytes$' >>> 

How to get a byte from a bytes object in Python?

>>> y = [80, 121, 116, 104, 111, 110, 32, 105, 115, 32, 101, 97, 115, 121] >>> print(y) [80, 121, 116, 104, 111, 110, 32, 105, 115, 32, 101, 97, 115, 121] >>> #create a bytes object >>> x1 = bytes([70, 111, 106, 94, 101, 100, 22, 95, 105, 22, 91, 87, 125, 135]) >>> print(x1) b'Foj^ed\x16_i\x16[W>\x87' >>> #is similar to the handling of lists, the index is defined in brackets >>> x = y[3] >>> print(x) 104 >>> print(chr(x)) h >>> #can also use negative indices to get a byte from bytes object >>> x = [-8] >>> print(x) [-8] >>> x = y[-8] >>> print(x) 110 >>> print(chr(x)) n >>> 

Create a bytearray object in Python

>>> #create a bytearray from a bytes object >>> x = bytearray(b"Python Bytes") >>> print(x) bytearray(b'Python Bytes') >>> #create a bytearray from a string defining the standard of coding >>> x = bytearray("Python Bytes", "utf8") >>> print(x) bytearray(b'Python Bytes') >>> #create a bytearray from a list of integers in the range 0 through 255 >>> x = bytearray([94, 91, 101, 125, 111, 35, 120, 101, 115, 101, 200]) >>> print(x) bytearray(b'^[e>o#xese\xc8') >>> 

Difference between bytes and bytearray object in Python

>>> #bytearray objects are a mutable counterpart to bytes objects >>> x = bytearray("Python bytearray", "utf8") >>> print(x) bytearray(b'Python bytearray') >>> #can remove items from the bytes >>> del x[11:15] >>> print(x) bytearray(b'Python bytey') >>> #can add items from the bytes >>> x[11:15] = b" object" >>> print(x) bytearray(b'Python byte object') >>> #can use the methods of mutable type iterable objects as the lists >>> x.append(45) >>> print(x) bytearray(b'Python byte object-') >>> 

Convert a bytes to bytearray

>>> #create a bytes object from a list of integers in the range 0 through 255 >>> x = bytes([105, 100, 107, 112, 132, 118, 107, 112, 200]) >>> print(x) b'idkp\x84vkp\xc8' >>> #generates a new array of bytes from a bytes object >>> x1 = bytearray(x) >>> print(x1) bytearray(b'idkp\x84vkp\xc8') >>> 

Slice of a bytes object in Python

>>> #create a bytes object >>> x = b"Python slice" >>> print(x) b'Python slice' >>> #b[start:stop] the start index is inclusive and the end index is exclusive. >>> x1 = x[2:6] >>> print(x1) b'thon' >>> #if the start index isn't defined, is starts from the beginning >>> x1 = x[-5:] >>> print(x1) b'slice' >>> #if the end index isn't defined, it goes until the end >>> x1 = x[:4] >>> print(x1) b'Pyth' >>> #if neither is defined, returns the full bytes object >>> x1 = x[:] >>> print(x1) b'Python slice' >>> 

Difference between bytes and string object

>>> # bytes objects are immutable sequences of integers, each value in the sequence >>> # string objects are immutable sequences of unicode characters. >>> x = "Python String" >>> y = b"Python String" >>> print(x) Python String >>> print(y) b'Python String' >>> # Found in unicode representation of characters but not in ascii >>> x = "Python" >>> y = bytes("Python", "utf8") >>> print(x) Python >>> print(y) b'Python' >>>

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>>> a = 'Hello World!' >>> # instead of using a[len(a)-1] >>> a[-1] '!' >>> # in combination with slicing >>> a[-5:-1] 'orld'

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Байты¶

Байтовые строки очень похожи на обычные строки, но с некоторыми отличиями.

Что такое байты? Байт — минимальная единица хранения и обработки цифровой информации. Последовательность байт представляет собой какую-либо информацию (текст, картинку, мелодию. ).

Создание байтовой строки¶

>>> b'bytes' b'bytes' >>> 'Байты'.encode('utf-8') b'\xd0\x91\xd0\xb0\xd0\xb9\xd1\x82\xd1\x8b' >>> bytes('bytes', encoding = 'utf-8') b'bytes' >>> bytes([50, 100, 76, 72, 41]) b'2dLH)' 

Функция bytes принимает список чисел от 0 до 255 и возвращает байты, получающиеся применением функции chr .

>>> chr(50) '2' >>> chr(100) 'd' >>> chr(76) 'L' 

Что делать с байтами? Хотя байтовые строки поддерживают практически все строковые методы, с ними мало что нужно делать. Обычно их надо записать в файл / прочесть из файла и преобразовать во что-либо другое (конечно, если очень хочется, то можно и распечатать). Для преобразования в строку используется метод decode :

>>> b'\xd0\x91\xd0\xb0\xd0\xb9\xd1\x82\xd1\x8b'.decode('utf-8') 'Байты' 

Bytearray¶

Bytearray в Python — массив байт. От типа bytes отличается только тем, что является изменяемым.

>>> b = bytearray(b'hello world!') >>> b bytearray(b'hello world!') >>> b[0] 104 >>> b[0] = b'h' Traceback (most recent call last): File "", line 1, in b[0] = b'h' TypeError: an integer is required >>> b[0] = 105 >>> b bytearray(b'iello world!') >>> for i in range(len(b)): . b[i] += i . >>> b bytearray(b'ifnos%>vzun,') 

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