Solving the problem of string encoding in Python2 and Python3

There are obvious differences between Python2 and Python3 in string encoding.

In Python2, strings cannot fully support international character sets and Unicode encoding. To address this limitation, Python2 uses a separate string type for Unicode data. To enter a Unicode string literal, add ' u ' before the first quotation mark. The normal string in Python2 is actually the encoded (non-Unicode) byte string.

In Python3, it is not necessary to include this prefix character, otherwise it is a syntax error, because all strings are already Unicode encoded by default.

$ Python2 instance:

>>> ' Zhang San ' #python2 automatically converts a string to an appropriately encoded byte string
' \xe5\xbc\xa0\xe4\xbf\x8a ' #自动转换为utf-8 encoded byte string

>>> u ' Zhang San ' #显式指定字符串类型为unicode类型, this type of string is not encoded, it holds the code ordinal of the character in the Unicode character set
U ' \U5F20\U4FCA '

>>> ' Zhang San '. Encode (' Utf-8 ') #python2 has been automatically converted to the Utf-8 type encoding, so the encoding again (Python2 will encode the string as ASCII or Unicode) will cause an error.
Traceback (most recent):
File "<stdin>", line 1, in <module>
Unicodedecodeerror: ' ASCII ' codec can ' t decode byte 0xe5 in position 0:ordinal not in range (128)

>>> ' Zhang San '. Decode (' Utf-8 ') #python2 can decode normally, the returned string class is a Unicode type that is not encoded
U ' \U5F20\U4FCA '

>>> B ' Zhang San ' # ' Zhang San ' has been python2 converted to utf-8 encoding, so it has been a byte string
' \xe5\xbc\xa0\xe4\xbf\x8a '

>>> print ' Zhang San '
Tom

>>> print u ' Zhang San '
Tom

>>> Print B ' Zhang San '
Tom

$ Python3 instance:

>>> ' Zhang San ' #python3的字符串默认为unicode格式 (no coding)
' Zhang San '

>>> u ' Zhang San ' #由于默认为unicode格式, so the string does not have to explicitly indicate its type as python2, otherwise it is a syntax error.
File "<stdin>", line 1
U ' Zhang San '
^
Syntaxerror:invalid syntax

>>> type (' Zhang San ') #python3中文本字符串和字节字符串是严格区分的, default to Unicode-formatted text string
<class ' str ' >

>>> ' Zhang San '. Decode (' Utf-8 ') #因为默认的文本字符串为unicode格式, so the text string has no Decode method
Traceback (most recent):
File "<stdin>", line 1, in <module>
Attributeerror: ' str ' object has no attribute ' decode '

>>> ' Zhang San '. Encode (' Utf-8 ') #将文本字符串编码, converted to encoded byte string type
B ' \xe5\xbc\xa0\xe4\xbf\x8a '

>>> type (' Zhang San '. Encode (' Utf-8 '))
<class ' bytes ' >

>>> print (' Zhang San '. Encode (' Utf-8 ')) #对于已编码的字节字符串, many of the features and methods of a text string are no longer available.
B ' \xe5\xbc\xa0\xe4\xbf\x8a '

>>>print (' Zhang San '. Encode (' Utf-8 '))
B ' \xe5\xbc\xa0\xe4\xbf\x8a '

>>> print (' Zhang San '. Encode (' Utf-8 '). Decode (' Utf-8 ')) #必须将字节字符串解码后才能打印出来
Tom

Solving the problem of string encoding in Python2 and Python3