Built-in functions, function variables, JSON

Tag: class res handles Chinese substitution GPO Site Map Object

A third-party variable is introduced to exchange the values of two variables:

A=1

b=2

C=0

C=a the value of a to c,c=1.

A=b the value of a to b,b=1.

B=c the value of C to b,b=1.

Print (A, b), running result: a=2 b=1

Exchange the value of two variables, only python can write this

A=1

b=2

The value of the A,b=b,a interchange variable

Print (A, b) run result: a=2 b=1

Exchange two values in a way that does not introduce a third-party variable

A=1
b=2
A=a+b  #a3
B=a-b #b1
A=a-b  #a2
Print (A, b), #运行结果: a=2 b=1
Built-in functions:
len int type str dict and so on are built-in functions
A=bin (1) decimal-to-binary, run result: 0b1 exists B so is the string type str
Print (A.replce (' 0b '))  replaces extra characters with spaces to display the correct binary values

Print (CHR) #打印数字对应的ascii       Run Result: A
Print (Ord (' A ')) #打印字符串对应的ascii码   Run Result: 65

Print (dir (1)) #打印传入对象的可调用方法, don't look at ' _xx_ '

A=[]
Print (dir (a))

Loop two lists at the same time, using a zip, the list with the smallest number to take the value

id=[1,2,3,0,4]
name=[' AA ', ' BB ', ' cc ', ' GG ']
name1=[' Zhang San ', ' John Doe ']
For i,k,s in Zip (id,name,name1):
    Print (i,k,s)  run Result: 1  AA  
                          2  BB  John Doe
Print (sorted (id,reverse=true)) #默认排序升序
Print (sorted (' 422435435 ', reverse=true))

Eval executes Python code, simple operations, defining data types and operations

A= ' + '

Print (eval (a)) Run Result: 2

Complex code cannot be executed, as shown below

A= ' def func (a):p
Print (eval (a))   operation error

exec executes complex code, and some automated code-execution sites use exec

S= ' Def a ():p rint (' sa ') '
EXEC (s)  runs complex code
A ()     run result: SA

   map and filter   
 The map loop invokes the function, placing the result of each function processing into a list 
 Def a (s): 
 If s%2==0: 
 return s 
 Else: 
 return ' OK ' 
 Xa=[x For x in range (one)] 
 Res1=map (A,XA) before a value is a function name, the next is a circular list loop xa call function A (the value of the XA loop) 
 Print (list (res1)) does not write list, Print a Map object 
 Run Result: [0,ok,2,ok,4,ok,6,ok,8,ok,10] 
  filter filter returns F Al    def A (s)   if s%2==0:    

return s If the input 0 return value is 0, not 0 is true, 0 is false so it is false;return true to determine that 0 is an even number is true will return to list--[0,2,4,6,8,10]
Else
Return False
Xa=[x for x in range (11)]
Res1=filter (A,XA)
Print (list (res1)) Run result: [2,4,6,8,10]

function is variable
def say (name):
Print (name)
Lyj=say say this function to lyj this variable lyj () equals say ()
Lyj (' lyj ') call function run Result: lyj
----------------------------------------------------------------
def add ():
Print (' Add product ')
Def view ():
Print (' View Products ')
def delete ():
Print (' Delete item ')
Choice=input (' Please enter the selection: ","). Stript ()
zd={
' 1 ': Add,
' 2 ': view,
' 3 ':d elete}
Zd[choice] () Zd[chice] is equivalent to a defined variable Add,view,delete
------------------------------------------------------------------
 processing JSON: The common data type, JSON string is the string is written into the file is a string, read out is also a string
Import JSON
d={' sa ': ' Ad ',
' ASD ': ' Dasdas '}
Res=json.dumps (D,indent=4,ensure_ascii=false) turns the dictionary, list to JSON string,indent how many indents, Ensure_ascii can display the Chinese
F=open (' sa ', ' w ', encoding= ' utf-8 ')
F.write (RES)
F.close ()

--------------------------------------------------------------------------
 Convert a JSON string to a list or dictionary with loads if JSON is a list style, it goes to the list type, and if the dictionary style, it goes to the dictionary type
f=open (' sa ', ' r ', encoding= ' utf-8 ')
R=f.read ()
Dict_r=json.loads (R)
The print (type (dict_r)) type is a dictionary
------------------------------------------------------------------------------
For file operations, dump writes files
F=open (' sa ', ' w ', encoding= ' utf-8 ')
Json.dump (d,f,ensure_ascii=false,indent=4)

Load Read file
F=open (' sa ', ' r ', encoding= ' utf-8 ')
Json.load (f)

Built-in functions, function variables, JSON