In fact, strings are also a data type. However, what is special about strings is that there is an encoding problem. The following article mainly introduces you to the relevant information on string operations and encoding Unicode in Python. Friends in need can refer to it. Let’s take a look together.
This article mainly introduces you to some knowledge about string operations and encoding Unicode in Python. I won’t say much below. Friends who need it can come and learn together.
String type
str
: Unicode string. Strings constructed using '' or r'' are all str, and single quotes can be replaced with double quotes or triple quotes. Regardless of how you specify it, there is no difference when it is stored internally in Python.
bytes
: Binary string. Since files in other formats such as jpg cannot be displayed using str, they are represented by bytes. Each byte of bytes is a number from 0 to 255. When printing, Python will display the part that can be expressed in ASCII as ASCII, which makes it easier to read. bytes supports almost all str methods except formatting, even including the re module
bytearray()
: Binary string that can be changed in place.
utf-8 encoding range
Number of bytes | Storage format | |
1 byte | 0xxxxxxx | |
2 bytes | 110xxxxx 10xxxxxx | ##0x0800~FFFF(2048 ~ 65535) |
1110xxxx 10xxxxxx 10xxxxxx | ##0x10000~1FFFFFF(65536 ~ 2097152) | |
11110xxx 10xxxxxx 10xxxxxx 10xxxxxx | ##0x2000000~0x3FFFFFF | 5 bytes |
0x4000000~0x7FFFFFFF) | 6 bytes | |
Byte order mark BOM |
BOM is the abbreviation of byte order marker,
Specifies the rules when encoding is written
Using 'utf-16-be' will not write a BOM header, but using 'utf-16' will write a BOM header.
>>> open('h.txt','w',encoding='utf-8-sig').write('aaa') 3 >>> open('h.txt','rb').read() b'\xef\xbb\xbfaaa' >>> open('h.txt','w',encoding='utf-16').write('bbb') 3 >>> open('h.txt','rb').read() b'\xff\xfeb\x00b\x00b\x00' >>> open('hh.txt','w',encoding='utf-16-be').write('ccc') 3 >>> open('hh.txt','rb').read() b'\x00c\x00c\x00c' >>> open('h.txt','w',encoding='utf-8').write('ddd') 3 >>> open('h.txt','rb').read() b'ddd'
Rules when reading
If the correct encoding is specified, the BOM will be ignored, otherwise the BOM It will be displayed as garbled characters or an exception will be returned.>>> open('h.txt','r').read() '锘縟dd' >>> open('h.txt','r',encoding='utf-8-sig').read() 'ddd'
Encoding and decoding
chr and ord
>>> ord('中') #20013 >>> chr(20013) #'中'
'\Uhhhhhhhh': Use 8-digit hexadecimal to represent a character
str and bytes, bytearray conversion
str.encode( encoding='utf-8')
bytes(s,encoding='utf-8')<br/>
bytes.decode(encoding='utf-8')<br/>
str(B, encoding='utf-8')<br/>
bytearray(string, encoding='utf-8')
bytearray(bytes)
Document encoding statement
Python uses utf-8 encoding by default.
: Indicates that the declaration document is latin-1 encoding.
Help function
sys.platform #'win32'
sys.getdefaultencoding() # 'utf-8'
sys.byteorder #'little'
s.isalnum() #s表示字符串
s.isalpha()
s.isdecimal
s.isdigit()
s.isnumeric()
s.isprintable()
s.isspace()
s.isidentifier() #如果字符串可以用作变量名,那么返回True
s.islower()
s.isupper()
s.istitle()