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[Python] # _ * _ coding: utf_8 _ import sys import OS class Graph (): def _ init _ (self, V, E): self. V = V self. E = E self. visited = [] self. dict = {} self. fd = open ("input.txt") def initGraph (self): self. visited = [0 for I in range (self. V + 1)] for I in range (self. e): f, t = map (int, self. fd. readline (). split () # f, t = map (int, sys. stdin. readline (). split () if self.
arguments to reference external functions return "It's a callable%s"% a # directly in intrinsic function using external function parameters Return add # returns the intrinsic function itself, without returning the result of an intrinsic function call running as follows: A1 = Test (1) # Dynamically generated a function that can record an external variable 3.
Python dict dictionary and some examples of value assignment reference (detailed description), pythondict
Recently, I am working on a very large database that needs to be searched by numerical value. So I thought of the dictionary in python, and I have never used dict.
List and tuple are the most commonly used)
I have
Python dictionary dict by value in keyAs we all know, the biggest advantage of dictionary dict is that it is very fast to find or insert, and does not want to list lists, as key increases more and more complex. But Dict need to occupy a large amount of memory space, in other words, the dictionary
Algorithm (hash).To ensure the correctness of the hash, the object as a key can not be changed. In Python, strings, integers, and so on are immutable, so you can safely use them as keys. The list is mutable and cannot be a key:>>> key = [1, 2, 3]'a list'Traceback (most recent call last): " " in 'list'" "Dictionary: Contains " "my_dict= {'name':'Kumata',' Age': 20,' Location':'Zhuhai'}#Output Key valueP
How to compile a Python script to convert a sqlAlchemy object to dict
This article mainly introduces how to compile a Python script to convert the sqlAlchemy object to dict. It mainly constructs a conversion method based on the Python model class. For more information, see
W
How to sort the Dict type key (keys) (Python 2.4 or later):Mydict = {'Carl': 40, 'Alan': 2, 'Bob': 1, 'Danny': 3} forKeyinchSorted (Mydict.iterkeys ()):Print "%s:%s"% (key, Mydict[key])Results:Alan:213Excerpt from Python faq:http://www.python.org/doc/faq/general/#why-doesn-t-list-sort-return-
can be queried either by the Get method or by key directly, but if the key does not exist, the error will be given, and get will give noneYou can add or change dict,dict (' key ') directly =valueYou can use the Pop method Dict.pop (Key[,default]) to delete the elements within the dict with the key value and return the value corresponding to the deleted key. If k
before index
Sort () to list remember orderL.sort (Cmp=none, Key=none, Reverse=false)--stable sort in place;CMP (x, y)-1, 0, 1
Reverse () reversalL.reverse ()--Reverse *in place*
Pop () deletes and returns the element value of the specified subscript, without specifying the default deletion of the lastL.pop ([index]), item-Remove and return item at index (default last).
Extend () extending the list by appending iteration elementsExtend list by appending elements from the iterabl
': ' Bob '}If key does not exist in Dict, it will be an error>>> dictionary["Age"]30>>> dictionary["ages"]traceback (most recent call last): File "To avoid a key that does not exist, there are two ways to avoid errors, one is to in determine if a key exists:>>> ' age ' in dictionarytrue>>> ' ages ' in DictionaryfalseThe second is the Get method provided by Dict, if key does not exist, you can return none,
I. A brief introduction to the dictionary The Dictionary (dict) is the only type of mapping in Python. He is composed of key-value pairs enclosed in {}. In Dict, key is unique. When saving, a memory address is calculated based on key. Then save the Key-value in this address. This algorithm is called the hash algorithm, so, remember, in the
This paper analyzes the application of dict,set,list,tuple in Python and its corresponding examples, which can help readers grasp the concept and principle. Specific as follows:
1. Dictionary (dict)
Dict surrounded by {}Dict.keys (), Dict.values (), Dict.items ()Hash (obj) returns the hash value of obj if it returns a
Python has built-in dictionaries: dict support, Dict full name dictionary, also known as map in other languages, dictionaries are another mutable container model and can store any type of object. Has a very fast search speed.A dictionary is a data structure referenced by a name or keyword, which can be a number, a string, a tuple, and this type of structure is al
Python-delete an element from a dictionary (dict)
You can delete a dictionary (dict) element in either of the following ways: dict. pop (key) and del dict [key].
Code
#-*-Coding: UTF-8-*-def remove_key (d, key): r = dict (d)
Reprinted from: http://blog.csdn.net/wzgbm/article/details/54691615First give a simple example, the time to test the list and dict find:ImportTime Query_lst = [-60000,-6000,- -,- -,-6,0,6, -, -,6000,60000] LST = [] dic = {} forIinchRange100000000): Lst.append (i) dic[i] =1Start = Time.time () forVinchQuery_lst:ifVinchLst:ContinueEnd1 = Time.time () forVinchQuery_lst:ifVinchDic:ContinueEnd2 = Time.time ()Print "List Search time:%f"% (End1-start)Print "
as an input collections = set([1,2,3]);s//{1,2,3}The set receives a parameter that is a list or tuple or other object that can be iteratedL = [x,y,z];s = set(L);But the elements in L x, y, z have any variable that will cause an error.adding elementsCan be added repeatedly, but not effectives.add(4);Delete Elements.remove(4);Set can be seen as a set of unordered and non-repeating elements in mathematical sense, so the two set can Do (intersection) and | (set) operations.The only difference betw
This function constructs a new dictionary from a mapped function object.Unlike the dict (**kwarg) function, a parameter input is a function object of a mapping type, such as a zip function,amap function. Examples:#dict () #以键对方式构造字典d1 = dict (one = 1, one = 2, a = 3) print (D1) #以映射函数方式来构造字典d2 =
as an input collections = set([1,2,3]);s//{1,2,3}The set receives a parameter that is a list or tuple or other object that can be iteratedL = [x,y,z];s = set(L);But the elements in L x, y, z have any variable that will cause an error.adding elementsCan be added repeatedly, but not effectives.add(4);Delete Elements.remove(4);Set can be seen as a set of unordered and non-repeating elements in mathematical sense, so the two set can Do (intersection) and | (set) operations.The only difference betw
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