Python Learning notes functions and classes

Python-like functions are also available for reuse only if the value of a piece of code is not reused can be used without a function

A general function can be defined like this:

defFunc (a,b=123,*arg,**args): forXinchArg#Arg is a list        Printx forX, yinchArgs.items ():#args is a dict        Printx, yPrint 'A:', aPrint 'B:', Bfunc (1,1,2,3,4,c=1,d=2) Results:234C1D2A:1B:1

Where A is the positional (required) parameter and B is an optional parameter

ARG is a parameter that accepts no limit, and Arg becomes a list when accepted.

Args is accepted a=1,b=2 ... this parameter, after receiving, args becomes a dict

Here are some function-related exercises (including some file operations),

" "Define a function Xulie (dirname,info) Parameter: dirname: path name, info: Data that needs to be serialized, function: serializes the info data to a random file in the dirname path. " "#Call the system function Os.listdir to get all the file names of the corresponding paths, store them in a list#then randomly get a file name in the list using random to change the fileImportRandomdefXulie (dirname,info): List_dir_name=[]     forXinchOs.listdir (dirname): List_dir_name.append (x) temp_name=list_dir_name[random.randint (0, Len (list_dir_name)-1)] F=open (Dirname+temp_name,'AB') F.write (info) f.close () Xulie ('d:\\test\\','This is a test')

defFunc_3 (name=none,**Kargs): Result=[]    ifLen (Kargs) >0: forX, yinchKargs.items (): Result.append ((x+':'+y)) result.insert (0, name)returnresultPrintFunc_3 (name='Lilei', age=' -', city='HK')
Results [' lilei ', ' city:hk ', ' age:20 ']

Class: A class like Java itself also has a constructor (__init__, class instantiation Call), destructor (__exit__, exit context Call, General and __enter__ method), there is a __del__ magic method, Called when Del deletes an instance of the class. There are also static methods that are called directly through a class call, rather than an instance of the class.

classText_sort (object):def __init__(self):Print 'This is init'    def __enter__(self):Print 'This is enter'    def __exit__(self,type,value,traceback):#Pass        iftype!=None:Pass        Else :            Pass        Print 'This is exit'    def __del__(self):Print 'This is del'@staticmethoddefStaticmethod ():Print 'This is Staticmethod'Text_sort.staticmethod () test1=Text_sort () with test1 as D:deld Result: this isStaticmethodthis isInitthis isEnterthis isExitthis is del

Classes of exercises, including classes worth passing, etc.:

" "Listinfo included methods: 1 List element additions: Add_key (KeyName) [KeyName: String or integer type]2 list element value: Get_key (num) [num: integer type]3 list merge: Update_list ( Lists) [list: Type]4 deletes and returns the last element: Del_key ()" "classListinfo (object):def __init__(self,*lists):#do not use magic parameter Self.args=args processing        #how to handle using magic parameters (direct write parameters without parentheses)self.args=[]         forXinchlists:self.args.append (x)defAdd_key (self,keyname):ifIsinstance (KeyName, str)orisinstance (keyname, int): Self.args.append (KeyName)returnTrueElse:            returnFalsedefGet_key (self,num): Result=[]        ifisinstance (num, int): forXinchSelf.args:ifLen (Result) <= num-1: Result.append (x)Else:                    Pass        returnresultdefupdate_list (self,list_in):ifisinstance (list_in, list): Self.args.extend (list_in)returnSelf.argsElse:            return 'Not list type'Self.argsdefDel_key (self):returnSelf.args.pop ()defGet_all (self):returnself.argslisttest=listinfo (4,222,111,33,4545,'SSS','332') Listtest.add_key (9999)PrintListtest.get_key (3)PrintListtest.update_list ([1])PrintListtest.del_key () results [4, 222, 111][4, 222, 111, 33, 4545,'SSS','332', 9999, 1]1

Python's advanced functions map,reduce and filter: They all work on a Literable object. Lambda is similar to anonymous functions, and in some places it can be interchanged with list generation.

foo=[12,24,36,48,11,33,55,77]map (Lambda x:x*2+5, foo) #将第一个函数分别作用于后面的literable对象, and returns a list result: [+, +, 101, 159]filter (Lambda x:x%2==0,foo) # The first function is used for the subsequent Literable object, which matches the result of the returned list result: [x, X,]reduce (Lambda x,y:x+y,foo) # The Literable Element 22 operation, and the result after each operation as the first parameter of the next operation result:296
[x for x in foo if x%2 = = 0] #结果与filter一样

Python Learning notes functions and classes