python dictionary of dictionaries

numbers and strings can be used as keys, lists, and other dictionaries.5, dictionary comparison: the first is the size of the dictionary, then the key, and finally the value6, built-in function ("Python core note" P172): Dict.get (Key,default=none), the key, the corresponding value returned, if the key does not exist,

empty the dictionary, empty only one operation, show Delete a dictionary with the del command [] #删除键是 entry for "002". Clear () #清空字典Features of the dictionary keyA dictionary value can take any Python object without restriction, either as a standard object or as a us

Python data types-tuples, commonly used dictionary operations, python data type dictionaryTuples The Python tuples are similar to the list. The difference is thatThe elements of the tuples cannot be modified.. The tuples use parentheses, And the list uses square brackets. Creating tuples is simple. You only need to add

Sort several data structures in Python, including lists, dictionaries, tuples, sets, and python data structures. List: shoplist = ['apple', 'mango', 'carrot', 'bana']Dictionary: di = {'A': 123, 'B': 'something '}Set: jihe = {'apple', 'pear ', 'apple '}Tuples: t = 123,456, 'Hello'1. ListEmpty list: a = []Function Method

dictionaryDel x (x is the dictionary name)5. Variable unpacking: items () Convert dictionary to key, value as a list of tuplesSyntax: X.items ()egX={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.items ()); ###[(' A ', 1), (' C ', 3), (' B ', 2)]Fetch key only: keys ()X.keys ()X={' A ': 1, ' B ': 2, ' C ': 3};p rint (X.keys ()); ###[' A ', ' C ', ' B ']Value only: VALUES ()X.values ()X={' A ': 1, ' B ': 2, ' C ':

collection? S.pop ()Randomly deletes an element in the collection and returns the deleted elementIv. other operations for sets and? Len (s)Show the length of set set? "1" in SDetects whether an element is a member of the collection S, returns a Boolean value? S.copy ()The shallow copy of the collection, not in-depth study here, will be said later? S.clear ()Empties all elements of a collectionDictionary :Dictionaries do not support indexing, slicingT

Basic Python tutorial for. Net programmers-usage of dictionaries [Third Day]Today I learned how to use the dictionary. The so-called dictionary is actually Key-value pair data. A dictionary has a unique Key that corresponds to a Value. The Key is unique and the value is not

dictionary (dict): The combination of unordered data that exists as a key-value pair is a dictionary, why do you say that, we all know that we have learned that the series such as lists, sets, etc. are only a single data can be stored, if you want to store the relevant data is more troublesome, For example, we want a person's name and his gender corresponding to the storage, this time using the list and so

(a) #把列表里的多个字符串拼接成一个字符串, this is not a good place to turn a list into a string, there are special uses, described below. Type (a) #查看a是列表还是字符串 '. Join (a) #把列表a的每个元素以空拼接起来, into a string. '-'. Join (a) #以-The string in a is spliced together. type (str (4)) #把数字类型int变成字符串string, The number is converted to a string because it is not allowed to write int to the file when it is written. f.writelines (a) # writes the list to the file. dela[6:11]# Delete list 6-10 rows--------------------------

Dictionaries are mutable and can store any number of Python objects, including another container type. A dictionary includes key pairs (called items) and their corresponding values. The Python dictionary is also known as an associative array or hash table. The general synta

The field is Python is the only key-value type in the dictionary, and is a very important data structure in Python, because it stores data in a hashed manner, with an O (1) complexity, which is very fast. The common uses of dictionaries are listed below. List of common methods in a

[::-1] #步进值-1, from the back forward value out[58 ]: ' EDCBA ' in[59]:a[::-2]out[59]: ' ECA ' in[61]:aout[61]: ' ABCDE ' In[ 60]:a[-4:-2]out[60]: ' BC ' in[62]:a[-2:-4:-1] from right to left, -2d-3c-4b no value,- 1 = right-to-left out[62]: ' DC ' An expression is a formula that joins different data (including variables, functions) with a number of operators to follow certain rules.Assignment operatorsThis article comes from "Plum blossom fragrance from bitter cold!" "Blog, be sure to keep this p

4.1 Dictionary use Dictionary: Data structures that refer to values by name, also known as values in the mapping dictionary, do not have a special order, but are stored in a specific key under the dictionary provided by the function:quickly find specific key-value correspondenceIn some cases,

': 0}d.items () dict_items ([' title ', ' Python webSite '), (' url ', ' http://www.python.org '), (' spam ', 0)])) it = D.items () len (IT) 3 (' spam ', 0) in Ittrue (' name ', ' admin ') in ItfalseKeys returns a dictionary view that contains the keys in the specified dictionaryD.keys () Dict_keys ([' title ', ' url ', ' spam ')Pop gets the value associated with the specified key and removes the key value

': ' Jinqiao Rd '}}7.setdefault is used to add a key (you can add a key if the key does not exist, unlike get, it will change the original dictionary)8.items IteritemsItems returned as a list of items in the dictionary, Iteritems returns an iteratorinfo={ ' Alice ':{ ' phone ': ' 2342 ', ' addr ': ' Taierzhuangrd '}, ' Bob ':{ ' phone ': ' 2242 ', ' addr ': ' Jinqiaord '} }printinfoprintinfo.items ()

, Popitem () randomly delete a pair of keys and values in the dictionary, the return value is a tuple, the elements of the tuple are deleted key value pairsD.popitem (), (k, v), remove and return some (key, value) pair as a 2-tuple; But raise Keyerror if D is empty.Dict1.popitem () (' C ', 3) dict1.popitem (' B ', 2)12, Iterkeys () returns an iterator to the dictionary keyIteritems () returns an iterator to