python full stack pass through --6- little knowledge summary

1, python2 and the difference between frequently used finishing python3

Python2 # 
Print 'ABC' 
# returns a list 
Range () 
# Returns a value generator , not list. Every time you build only one value, avoid temporary use a lot of memory 
xrange () # Builder 
# input 
raw_input (...) 

# python3 
Print ( 'abc') 
# returns an iterator value , you need to generate a list you need to use list ( the Range (...)) 
the Range () 
the INPUT (...)

2, copy == comparison value comparison is equality, the memory address comparing id (Content)

In Li1 = >>> [l, 2,3 ]
 >>> = LI2 in Li1
 >>> Pring (ID (in Li1), ID (LI2))
 >>> Print (ID (in Li1), ID (LI2))
 2,472,533,256,584 2,472,533,256,584 # presence decimal numbers and strings pools, pool the decimal range, are using the same memory address 
# numbers 256 ~ -5 
>>> = I1. 6 
>>> = I2. 6 
>>> Print (ID (I1), ID (I2))
 140,717,920,019,440 140,717,920,019,440 
>>> I1 = 300 
>>> 300 I2 = 
>>> Print (ID (I1), ID (I2))
 2472536947344 2472536947248 
>>> I1 = 256 
>>> 256 I2 = 
>>> Print (the above mentioned id (I1),
id(i2))
140717920027440 140717920027440
>>> i1 = 257
>>> 


>>> i2 = 257print(id(i1),id(i2))
2472536947344 2472536947248
>>> i1 = -5
>>> i2 = -5
>>> print(id(i1),id(i2))
140717920019088 140717920019088
>>> i2 = -6
>>> i1 = -6
>>> print(id(i1),id(i2))
2472536947344 2472536947248

 

# Strings: 1, can not have special characters 
#          2, s * 20 or the same address, s * After the 21 are two addresses ( . To be verified, during the test, more than 1 * are estimated to be changes in the different versions of lead ) 
>>> S1 = ' 121212asdasdasdadasdasdasdadadqrjladksfjaiodfu ' 
>>> S2 = ' 121212asdasdasdadasdasdasdadadqrjladksfjaiodfu ' 
>>> Print (ID (S1), ID (S2))
 2472537146064 2472537146064 
>>> S1 = ' 121212asdasdasdadasdasdasdadadqrjladksfjaiodfu @ ' 
>>> S2 = ' 121212asdasdasdadasdasdasdadadqrjladksfjaiodfu @ ' 
>>> Print (ID (S1),
id(s2))
2472537146160 2472537146064#

 list、dict、tuple、set
# list
>>> l1 = [1,]
>>> l2 = [1,]
>>> print(l1 is l2)
False
>>>
>>> l2 = l1
>>> print(l1 is l2)
True

 

3, character set encoding

ASCII 
            A: 00000010. 8 bits of a byte 

unicode A: 00000000 00000001 00000010 00000100 32 four bit bytes 
            in: 0,000,000,000,000,001 0,000,001,000,000,110 32 four byte 


utf-8 A: 00100000 8 bits of a byte 
          are: 00000001 0,000,001,000,000,110 24 three bytes 


gbk a: 00000110 8 bits of a byte 
         in which: 0,000,001,000,000,110 two 16-bit bytes 
1, between the various binary coding, can not recognize each other, it will be garbled. 
2, file storage, transmission, is not unicode (only utf-8 utf-16 gbk, gb2312, asciid etc.)



 Py3: 
    STR is unicode encoded in memory. 
        Type bytes 
        for English: 
             STR: Expressions: s = 'beer' 
                    encoding: Unicode 
            bytes: Expressions: s = b'beer ' 
                    encoding: utf-8 gbk. . . . 

        For Chinese:
             str: Expressions: s = 'Xiong' 
                    encoding: Unicode 
            bytes: Expressions: s = b '\ xe9 \ x9b \ x84 \ xe5 \ xa4 \ xa7' 
                    encoding: utf-8 gbk. . . .

>>> s = 'beer'
>>> s1 = b'beer'
>>> print(s,type(s))
beer <class 'str'>
>>> print(s1,type(s1))
b'beer' <class 'bytes'>
>>> 
>>> 
>>> s = '雄大'
>>> print(s,type(s)
      )
雄大 <class 'majestic'
>>> S1 = B>'Str'
SyntaxError: bytes can only contain ASCII literal characters.
>>> 
>>> 
>>> s1 = s.encode('utf-8')
>>> print(s1)
b'\xe9\x9b\x84\xe5\xa4\xa7'
>>> s1 = s.encode('gbk')
>>> print(s1)
b'\xd0\xdb\xb4\xf3'