Python Finishing-day4

1.Python Foundation

2. Basic data type: Str,dict,list,int

s= "WZC" =>str

3. Functional programming

function definition

Built-in functions

File processing

Attention:

Li=[11,22,33,44]def Fi (ARG):    arg.append (in) fi (LI) print (LI) li=fi (LI) print (LI)

It is necessary to note that the function returns none by default, so we need to refer to it by parameter when we use it.

4. Other

Ternary operations

Lambda expression

s= "haha" bytes (s,encoding=utf-8) false:[],{}, (), none,0, ""

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcdef F1 ():    passprint (Callable (F1))

英文说明: Check whether object is callable. If return true,object still may fail, but if return false, calling object Ojbect will never succeed.

Note : The class is callable, and an instance of the class implements the __call__ () method to invoke.

version : This function is available in the python2.x version. However, it was removed in the python3.0 version and was re-added in the later version of python3.2.

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzca=chr (+) print (a) B=ord ("B") print (b)

ASCII code can be found , can also be reversed to find , the number converted to letters, letters converted to numbers, which need to rely on the corresponding ASCII code relationship

Generate random numbers

Andom. Randrange This is the range of random numbers . If you combine with CHR, there will be random letters, but be aware that Acsii is a range, and65-90 is the range of uppercase letters .

The scope of this is 1<=i<5 , so you need to add a bit later when you type.

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcimport randomli=[]num=0for  i in  range (6):    r= Random.randrange (0,5)    if r = = 2 or r = = 4:        c=random.randrange (0,9)        b=str (c)        Li.append (b)    else:        c=random.randrange (65,91)        B=CHR (c)        Li.append (b)        num=0re= "". Join (LI) print (re)

This is a random verification code that produces a combination of numbers and English.

1. read file contents open,str to memory

2.python, string = "compile =" Special code

3. Execute code

Compile, which is used to compile the code.

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcs= ' Print ("123") ' #将字符串编译成python code 

R=compile (S, "string", "exec") # There's  no relationship between exec and the following  

Print (R) Exec (r) #执行Python code 

Single: Compile the above code into a one-line Python program

Eval: Compiling into an expression

EXEC: Compiling to the exact same pattern

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcr1=exec ("7+8+9")
Print (R1)
R2=eval ("7+8+9") #eval: This function allows you to convert a string to an expression, and to perform the following

Print (R2)

EXEC: better than eval , exec can execute all Python code and strings, and eval can only execute expressions

But one more function of eval than exec is that Eval has a return value, and exec has no

Quick view of what features the object provides

Print (dir (list))

Paging function

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcr=divmod (99,10) print (R)

The paging function is the calculation of the quotient, while the remainder can be obtained. returned is a meta-ancestor

Object is an instance of a class

Object "WZC", "www" their class is "str"

objects [11,22,33],["W", "Z", "C"] their class is List

And so on Dict's class, everybody knows.

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzca=["A", "B"]r=isinstance (a,list) print (R)

Isinstance, Determines whether an object is an instance of a class

The difference between this and type is that isinstance can be looked up, used in the base class, and type cannot be

Filter (functions, objects that can be iterated)

Lists, meta-ancestors, dictionaries, are objects that can be iterated

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcli=[11,22,33,44,]def F1 (ARG): If arg > 22:return Tru Eret=filter (f1,li) Print (list (ret))

Inside the filter, the second parameter is first cycled and then the first parameter is executed inside each loop

#filter内部, loop the second parameter #result=[] #for  item in the second parameter #     r= the first argument (item) #    if r:#        result (item) #return result# The second parameter of the filter loop function allows each loop element to execute a function if the function returns Ture, indicating that the element is valid

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcli=[11,22,33,44,]def F1 (ARG):    if arg >:        return True Ret=filter (f1,li) Print (list (ret) li=[11,22,33,44,]ret1=filter (lambda a:a>33,li) print (list (RET1)) Ret=map ( Lambda a:a+100,li) Print (list (ret))

This allows the same functionality to be achieved with La MBDA expressions

Map (functions, objects that can be iterated (something for Loop))

Filter: function returns ture and adds elements to the result

Map: Add a function return value to the result

Frozenset (): Immutable collection

Globals (): All Global variables

Locals (): All local variables

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcs= ' wzcceqwediojdfiosjdjkfnjkwdhuiahjcnzkxcnx ' Print (hash (s))

At the time of storage, more is to save a hash value, other languages are basically this

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcs= "haha" print (len (s)) b=bytes (s,encoding= "Utf-8") print (len (b))

Python3 is by character, Python2 is in bytes , Python3 can be passed by character, or it can be viewed by byte

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcs= ' {"K1": "v1"} ' #里面必须是双引号, single quote not print (type (s), s) Import jsonn= Json.loads (s) #将一个字符串转换成Python基本数据类型 {},[]print (Type (n), N)

To convert through JSON , the elements inside must be enclosed in double quotes and single quotes .

Max (): Max

Min (): min

SUM (): sum

Memoryview (): A class related to memory address

Object (): A class that is a sub-class of all classes

POW (): Seeking square, equivalent to 2**10==pow (2,10)

Reverse (): Flip, List.reverse () ==reverse (list)

Round (): Rounding

Slice (): Take interval, s= "12345", print ([0:2:2]) function same

Sorted (): Sort, List.sort () =sorted (list)

Built-in functions that need to be mastered

Adorner : decorating a function from the outside

Open Closure principle

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzc# def f1 (): #     print ("F1") # def f2 (XXX): #     xxx () # F2 (F1) def o Uter (func):    def Inter (*args, **kwargs):        print ("before")        R=func (*args, **kwargs)        print ("after")        return R    return inter@outerdef F1 (ARG):    print (ARG)    return "haha" r=f1 ("Heihei") print (r) print ("#") @ Outerdef F2 (A1,A2):    print (A1,A2) F2 (11,12)

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcdef F1 (): Print ("F1") def f2 (XXX): xxx () f2 (F1)

A function can be called as a parameter, and the F 1 inside is executed.

def outer (func): Def Inter (): print ("before") func () print ("after") return Inter@outerdef F1 (): Print ("F1") F1 ()

@+ function

Function:

1, automatically executes the outer function, and the following function name F1 as a parameter passed

2, the return value of the outer function is re-assigned to F1

#!/usr/bin/env python#-*-coding:utf-8-*-# author:wzcdef Outer (func): def Inter (*args, **kwargs): Print ("Befo    Re ") R=func (*args, **kwargs) print (" after ") return R return inter@outerdef F1 (ARG): Print (ARG) return "haha" r=f1 ("Heihei") print (r) print ("#") @outerdef F2 (A1,A2): print (A1,A2) F2 (11,12)

When the fi has parameters, the adorner outer also needs to follow the parameters to execute

When there are multiple parameters, you can use * * to handle

Python Finishing-day4