Detailed explanation of python string, bytes, bytearray types-Python Tutorial-php.cn

Detailed explanation of python string, bytes, bytearray types

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Release： 2017-12-18 09:17:47

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Python3 makes a distinction between text and binary data. The text is Unicode encoded, str type, used for display. The binary type is bytes type, used for storage and transmission. bytes is a sequence of bytes, and str is a sequence of unicode. This article mainly introduces the python string type bytes type bytearray type. Friends who need it can refer to it. I hope it can help everyone.

1. str type:

 >>> s = u'你好'
 >>> s
 '你好'
 >>> type(s)
 <class &#39;str&#39;>

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bytes type:

 >>> b = b'abc'
 >>> b
 b'abc'
 >>> type(b)
 <class &#39;bytes&#39;>

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2. The conversion relationship between str and bytes: str-->encode()-->bytes-->decode()-->str

Conversion method one: encode( ), decode()

 >>> a = u'你好'
 >>> b = a.encode('utf-8')
 >>> b
 b'\xe4\xbd\xa0\xe5\xa5\xbd'
 >>> type(b)
 <class &#39;bytes&#39;>
 >>> new_a = b.decode('utf-8')
 >>> new_a
 '你好'
 >>> type(new_a)
 <class &#39;str&#39;>

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Conversion method two: bytes(), str()

 >>> a = u'你好'
 >>> b= bytes(a, encoding='utf-8')
 >>> b 
 b'\xe4\xbd\xa0\xe5\xa5\xbd'
 >>> type(b)
 <class &#39;bytes&#39;>
 >>> new_a = str(b, encoding='utf-8')
 >>> new_a
 '你好'
 >>> type(new_a)
 <class &#39;str&#39;>

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3. Bytearray type

The bytearray class is a variable sequence in the range 0 < = x < 256.

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

• If it is a string, then you must also give the encoding (and optionally an error) Parameters; bytearray() then uses str.encode() to convert the string to bytes.
• If it is an integer, then the array will have this size and will be initialized with null bytes.
• If it is an object conforming to the buffer interface, the byte array will be initialized using the object's read-only buffer.
•If it is an iterable, then it must be an iteration of integers in the range 0 < = array of 0.

When the source parameter is a string:

 >>> b = bytearray(u'你好', encoding='utf-8')
 >>> b
 bytearray(b'\xe4\xbd\xa0\xe5\xa5\xbd')
 >>> type(b)
 <class &#39;bytearray&#39;></p>
<p></p>When the source parameter is an integer: <p></p>
<p></p>
<pre class="brush:php;toolbar:false">
 >>> b = bytearray(5)
 >>> b
 bytearray(b'\x00\x00\x00\x00\x00')
 >>> type(b)
 <class &#39;bytearray&#39;>

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When the source parameter is an iterable object, then the elements of this iterable object must conform to 0 <= x < 256:

 >>> b = bytearray([1, 2, 3, 4, 255])
 >>> b
 bytearray(b'\x01\x02\x03\x04\xff')
 >>> type(b)
 <class &#39;bytearray&#39;

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4. The difference between bytes and bytearray

bytes is immutable, the same as str. bytearray is variable, the same as list.

 >>> b = bytearray()
 >>> b
 bytearray(b'')
 >>> b.append(10)
 >>> b
 bytearray(b'\n')
 >>> b.append(100)
 >>> b
 bytearray(b'\nd')
 >>> b.remove(100)
 >>> b
 bytearray(b'\n')
 >>> b.insert(0, 150)
 >>> b
 bytearray(b'\x96\n')
 >>> b.extend([1, 3, 5])
 >>> b
 bytearray(b'\x96\n\x01\x03\x05')
 >>> b.pop(2)
 1
 >>> b
 bytearray(b'\x96\n\x03\x05')
 >>> b.reverse()
 >>> b
 bytearray(b'\x05\x03\n\x96')
 >>> b.clear()
 >>> b
 bytearray(b'')<p></p>5. Conversion of bytes and bytearray<p></p>
<p></p>
<pre class="brush:php;toolbar:false">
 >>> b = b'abcdef'
 >>> bay = bytearray(b)
 >>> bay
 bytearray(b'abcdef')
 >>> b = bytes(bay)
 >>> b
 b'abcdef'

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6. Conversion of bytearray and str

 >>> a = 'abcdef'
 >>> b = bytearray(a, encoding='utf-8')
 >>> b
 bytearray(b'abcdef')
 >>> a = b.decode(encoding='utf-8')
 >>> a
 'abcdef'

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