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1. python2, the difference python3
python2 ascii code python3 UTF-8
python2 prin support without parentheses is not supported by python
There are also python range Xrange (generator) python ordered list of range only
python in user interaction raw_input python3 as input
2. =, ==, is (relatively memory address), id (content) view id
= Assignment
== compare values for equality
It is relatively memory address
LI1 = [1,2,3]
li1 = li2
print(li1 is li2)
print(id(li1),id(li2))
3. breakdown, a small string of data values
A digital value corresponding to the variable range of -5-256 consistent, using a common memory address
String range using the same memory address can not contain special characters 1. 2.s * 20 same address, s * 21 addresses two
Il = 6
i2 = 6
print(id(i1),id(i2))
In addition to digital and str list and dict tuple set no small data pool concept
4. encoding
ascii code A: a one byte character represented by one byte 8 0000100
unicode A: a character is represented by four bytes 32 00010001 0001010 0,010,001,000,101,010
utf-8 A: a character represented by one byte in the 8 00101001: a Chinese represented by three bytes 24 0,101,010,100,100,100 00101001
gbk A: a character represented by one byte in the 8 01010101: 16 represents a Chinese two bytes 0,101,010,100,100,101
Between individual coding binary 1 is not recognized each other, will be garbled
2. The storage and transmission of documents can not be unicode, only utf-8 or utf-16 or gbk or gbk2312 unicode or ascii because too much traffic occupancy
python3：
str python3 the encoding in memory is unicode
str bytes data type to be transmitted or stored, if need be converted to a type of data bytes
For English speaking
forms str str = 'alex'
01010101 unicode encoding
bytes form of s = b''alex '(represented preceded b)
Encoding: 00100100 utf-8 gbk gk2312
For Chinese
str manifestation str = 'China'
01010101 unicode encoding
bytes form of s = b'x \ e91 \ e91 \ e01 \ e21 \ e31 \ e32 '(16 hex)
Encoding: 00100100 utf-8 gbk gk2312
str convert bytes English
s1 = ‘alex’
s11 = s1.encode('utf-8')
print(s11)
str conversion bt \ ytes Chinese
s2 = 'Chinese'
s22 = s2.encode('utf-8')
print(s22 )
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