python 浅谈小数据池和编码

根据提示我们从官??档找到了这样的说法：
A Python program is constructed from code blocks. A block is a piece of
Python program text that is executed as a unit. The following are blocks: a
module, a function body, and a class definition. Each command typed
interactively is a block. A script file (a file given as standard input to
the interpreter or specified as a command line argument to the interpreter)
is a code block. A script command (a command specified on the interpreter
command line with the ‘-c‘ option) is a code block. The string argument
passed to the built-in functions eval() and exec() is a code block.
A code block is executed in an execution frame. A frame contains some
administrative information (used for debugging) and determines where and
how execution continues after the code block’s execution has completed.

粗略的翻译:
python程序是由代码块构成的. ?个代码块的?本作为python程序执?的单元.
代码块: ?个模块, ?个函数, ?个类, 甚?每?个command命令都是?个代码块. ?个?件也是?
个代码块, eval()和exec()执?的时候也是?个代码块

s = ‘alex‘
print(id(s)) # 4326667072

对于整数， Python官??档中这么说：
The current implementation keeps an array of integer objects for all
integers between -5 and 256, when you create an int in that range you
actually just get back a reference to the existing object. So it should be
possible to change the value of 1. I suspect the behaviour of Python in
this case is undefined.

对于字符串：
Incomputer science, string interning is a method of storing only onecopy of
each distinct string value, which must be immutable. Interning strings
makes some stringprocessing tasks more time- or space-efficient at the cost
of requiring moretime when the string is created or interned. The distinct
values are stored ina string intern pool. –引?维基百科

a = 1000
b = 1000
print(a is b)
注意. 在py?件中.得到的结果是True, 但是在command中就不是了.

s = "alex"
print(s.encode("utf-8")) # 将字符串编码成UTF-8
print(s.encode("GBK")) # 将字符串编码成GBK

结果:
b‘alex‘b‘alex‘

s = "中"
print(s.encode("UTF-8")) # 中?编码成UTF-8
print(s.encode("GBK")) # 中?编码成GBK

结果:
b‘\xe4\xb8\xad‘
b‘\xd6\xd0

s = "我叫李嘉诚"
print(s.encode("utf-8")) #
b‘\xe6\x88\x91\xe5\x8f\xab\xe6\x9d\x8e\xe5\x98\x89\xe8\xaf\x9a‘
print(b‘\xe6\x88\x91\xe5\x8f\xab\xe6\x9d\x8e\xe5\x98\x89\xe8\xaf\x9a‘.decode("utf-8")) # 解码

s = "我是?字"
bs = s.encode("GBK") # 我们这样可以获取到GBK的?字
# 把GBK转换成UTF-8
# ?先要把GBK转换成unicode. 也就是需要解码
s = bs.decode("GBK") # 解码
# 然后需要进?重新编码成UTF-8
bss = s.encode("UTF-8") # 重新编码
print(bss)