python dict comprehension

In python, common objects are used as Dictionary classes (dict ). Currently, I know two methods: 1. The defined class inherits the dict class. For example Class A (dict): pass A = () A ['name'] = 12 2. Add a custom class _ Setitem _ () _ getitem _ () method Class A: def _ init _ (self, cfg = {}):Self. cfg = cf

Tuple, list, dict, and pythontuple in Python ------------------------------- Updating -------------------------------------- Tuple ): Tuples are commonly represented by parentheses (). The elements are identified by commas. 1 # define a tuple 2 3 # tuple = 'A', 4 5 tuple = ('A', 'B', 'C', 'D', 'E ', 'F', 'G') 6 7 # In general, after defining a tuples, you cannot add or modify the elements of the tuples,

1. key cannot be used with list and setBecause the list is variable, it cannot be a key. If the use will be errorBut tuples can do key2. Traversal method for inch somedict: Passfast, But if you want to delete an element that causes an error, the following error occurs#here, Initialize a dict .>>> d = {'a': 1,'b'70A'C': 1,'D': 0}#the intention is to traverse the dict and find that the value of the eleme

Two methodsShortcuteval (str)>>> user = "{‘name‘ : ‘jim‘, ‘sex‘ : ‘male‘, ‘age‘: 18}">>> type(user)‘str‘>>>> b=eval(user)>>> >>> b{‘age‘: 18, ‘name‘: ‘jim‘, ‘sex‘: ‘male‘}>>> type(b)‘dict‘>With regard to Eval (), the official demo is interpreted as: the string str is evaluated as a valid expression and returns the result of the calculation.In fact, there are limitations, such as dealing with multidimensional dictionaries.JsonAnother professional conve

don't have this keyDic.get (key, return value) View 2: None returns none, specifying what to returnDic.setdefault (Key) View 3: No then return none1DIC = {"K1":"v1","K2":"v2","K3":"v3"}2 forIinchDIC:3 Print. IO4 Print(dic["K1"])5 Print(Dic.get ("K2"))6 Print(Dic.setdefault ("K3"))3. Other operations of the dictionary:Keys gets to all the keys that exist in a high-imitated listValues gets to all the values that exist in a high-imitated listItems gets to all the key values in the form of a m

Dictionary: Dict1. The dictionary is the only type of mapping in Python and consists of value pairs enclosed in {};2, the dictionary key is unique, at the time of saving, according to key to calculate a memory address, how to put value in this memory, this is called the hash algorithm;3. The key in the dictionary must be hashed (immutable data type Str,int,tuple,bool)4. Value in the dictionary can be stored in any data type5, the dictionary is also di

A list or Dict object cannot be written directly, and a typeerror appears. First, write list to TXT file: iptable = [' 158.59.194.213 ', ' 18.9.14.13 ', ' 58.59.14.21 '] fileobject = open (' SampleList.txt ', ' W ') for IP in Iptable: fileobject.write (IP) fileobject.write (' \ n ') Fileobject.close () Ii. writing Dict objects to JSON files Need to import JSON, convert

1. Dictionary Dict1.1Dictionary Definitions>>> d={' Adam ': Up, ' Lisa ': $, ' Bart ': 59}1.2Dictionary Access1.2.1key Method AccessDict[key]>>> d[' Adam ']95Determine if key is--in in Dict(can only Judge key)>>> D{' Lisa ': $, ' Adam ': Up, ' Bart ': 59}>>> ' Paul ' in DFalse>>> ' Lisa ' in DTrue>>> in DFalse1.2.2get Method AccessDict.get (Key) The dict itself provides a GET method that returns none when k

whitespace charactersString.punctuation some punctuationMethod of the String module:Capitlize (s) returns the first uppercase string of sCapwords (s,sep) with Sep to split S, and then split out the first letter of each part of the capital, and then use Sep to connect these parts, Sep default is a spaceCenter (S,width[,fllchar]) put s in width (an int number) long string solemn, both sides with Fillchar fill. can be used to generate a delimiter in a text file.Count (S,sub[,start[,end]]) returns

# Conditional JudgmentThe role of Elif:else ifNote: "Colon"BMI =w/(h*h)If bmiPrint (' lighter ')Elif bmiPrint (' normal ')else BIM:Print (' obese ')# loopsFor x in XS a bit like the C # foreachRange () generates an integer sequence, range (101) generates an integer sequence of 0~100While loopFind differentOnen = one while n>10: n-1 print(n)Twon = ten while n >: = n-1 print('1', N)The difference between one and two,,,#dict和setDict Dictionar

Now I know there are two ways to do this:1 class inheritance Dict classes definedFor exampleClass A (dict): PassA = A ()a[' name '] = 122 Adding a custom class__setitem__ () __getitem__ () methodClass A:def __init__ (self, cfg={}):self.cfg = cfgdef __setitem__ (self, Key, value): self.cfg[key] = Valuedef __ge Titem__ (self, key): Return self.cfg[key]a = A () a[' B '] = 2print (a[' B '))Output:2[finished in

. ReadLine()) prints The single row of the current cursorprint (FFF. ReadLines ()) prints everything after the cursor ( multiline ) F. close () close Open file f.tell () file cursor position (medium: 3, UK: 1) F. seek (3) artificially cursor is positioned to 3 F. flush () contents from memory written to disk F.truncate([size]) intercepts the file , the truncated byte is specified by size, and the current file location is assumed by default. Os. Rename (' curr

efficiency of the list deduction is actually the same as for the for.def Add (x): return for inch Array] # loops, Best of 3:180 us per loopAs always: simple cyclic mapping operations, we recommend the form of a list deduction, which is more efficient and faster. Complex cyclic mapping operations, we recommend using a For loop, which makes the code easier to read and understand. And for the map method, we think this is an outdated way of writing, should be used sparingly, not even.Reference