DescribeThe Python Dictionary (Dictionary) SetDefault () function is similar to the Get () method, and if the key does not already exist in the dictionary, the key is added and the value is set to the default value.GrammarSetDefault () method syntax:Dict. SetDefault(key,default=None) Parameters
Key--Th
DescribeThe Python dictionary (Dictionary) get () function returns the value of the specified key if the value does not return a default value in the dictionary.GrammarGet () method syntax:Dict. Get(key,default=None) Parameters
Key--The keys to find in the dictionary.
Default-Returns the default va
[Python-dictionary usage] Three methods for creating a dictionary: python3
# Create an empty dictionary empty_dict = dict () print (empty_dict) # Use ** kwargs variable parameters to input keywords to create a dictionary a = dict (one = 1, two = 2, three = 3) print (a) # Pa
problem: construct a dictionary, which is a subset of another dictionaryAnswer: The simplest way is to use a dictionary derivationEG1:1.>>>prices = {' ACME ': 45.23, ' AAPL ': 612.78, ' IBM ': 205.55, ' HPQ ': 37.20, ' FB ': 10.75}>>>P1 = {Key:value for key, value in Prices.items () if value > 200}>>>p1{' AAPL ': 612.78,' IBM ': 205.55}2.dictionary derivation
Yes3Dictionary method, which returns a list-like value, corresponding to the dictionary's key, value, and key-Value pairs:Keys ()、VALUES ()AndItems ()。 The values returned by these methods are not real lists, they cannot be modified, noAppend () method. However, these data types ( dict_keys,dict_values, and Dict_items, respectively ) can be used for a for loop. To see how these methods work, enter the following code in the interactive environment: P
#!/usr/bin/env python
#-*-coding:utf-8-*-
# 1, Scenario 1: Using built-in functions sorted from
random import randint
d = {X:rand Int (m) for x in ' Xadfyz '}
# Converts a dictionary to a list containing tuples, using the ZIP function results such as: [(b, ' a '), (E, ' d '), (+, ' F '), (+, ' Y '), ($, ' X '), (+, ' z ')]
# result = Zip (D.values (), D.keys ()) Result
= Zip (D.itervalues (), D.keys ())
Python basics 2-dictionary, python2-dictionary
Dictionary
Dictionary is another variable container model that can store any type of objects.
Each key-value (key => value) pair of the dictionary uses the colon (:), And each pair is
1. Dictionary: in Python, a dictionary is a series of key-value pairs. Each key is associated with a value, and you can use the key to access the value associated with it. The values associated with the key can be numbers, strings, lists, and dictionaries. You can actually use any Python object as a value in the dictio
DescribeThe Python dictionary (Dictionary) items () function returns an array of traversed (key, value) tuples in a list.GrammarThe items () method syntax:Dict.items () Parameters
NA.
return valueReturns an array of (key, value) tuples that can be traversed.InstanceThe following example shows how to use the items () function:#!/usr/bin/pythondict = {' Nam
1. Dictionary definition, key unique, value arbitrarydic={key0:value0,key1:value1}2. Outputprint(dic[key0])>>:value03. Traversing a dictionary3.1keys () traverse the key in the dictionarydic={‘name‘:‘zhangsan‘,‘age‘:20}for k in dic.keys(): print(k)>>:nameage 3.2values () traverse the value in the dictionarydic={‘name‘:‘zhangsan‘,‘age‘:20}for v in dic.values(): print(v)>>:zhangsan203.3items () traversing the key,value in the dictionar
SetDefault () methodParameters
Key--The value of the lookup.
Default-key is not present, set the defaults.
GrammarSetDefault () method syntax:Dict. SetDefault(key,default=None) DescriptionIf the parameter key does not exist in the dictionary, the key is added and the value of the key is set to default.If the parameter key already exists, do not take any actionreturn valueThe method does not have any return value.InstanceWhen
Welcome to follow Me blog: Cloud DreamerDescriptionThe Python Dictionary items () method returns a traversal (key, value) array of tuples in a list form (not a direct list, to return a list value and also call the list function).GrammarDict.items()Parameters
NA
return valueReturns an array of traversed (key, value) tuples as a list.ExampleExample code:= {‘Google‘‘www.google.com‘‘Runoob‘‘www.ru
Dictionary traversal is the traversal of key, and the order of key selection is unordered:def print_hist (h): For C in H:print C, H[c]Dict reverse lookup and throws an exception:def reverse_lookup (d, v): for K in d:if d[k] = = V:return k raise ValueError, ' element not found 'Initialize Dict:ENG2SP = {' One ': ' Uno ', ' both ': ' dos ', ' three ': ' Tres '}Dict lengthLen (ENG2SP)In operator to determine if a specific key is included>>> ' one ' in en
'), ((), ' C '), ((a), (' d '), (+, ' e '), (+, ' F '), ((a), ' G '), then orted sortSorted (z)The Third Way: [(A1,B1,C1), (A2,B2,C2), (A3,B3,C3), (A4,B4,C4) ...] The sorted function allows you to sort the specified elements of this collection.Sorted (D.items (), Key=lambda x:x[1]), the first argument is a list that needs to be sorted, and the second parameter is the order of the specified key (the element of each item in the list).Explanation of this code: D.items () returns a list [(' A ', '
Dictionary (dictionary)
We've all used a language dictionary to find the definition of a word we don't know. A language dictionary provides a standard set of information for a given word, such as Python. This system associates the definition and other information with the ac
Python self-study day-Two day (2)-python-list-tuples-dictionary, python-
ListFormat: name = []Name = [name1, name2, name3, name4, name5]
# List operations
Name. index ("name1") # query the name of the specified value. count ("name1") # query the name of the total number of specified values. clear ("name") # clear the l
Basic python Tutorial Study Notes --- (4) dictionary and python Study NotesSequence is a data structure in python, and ing is another. Mapping refers to a value by name. The only ing structure built in python is a dictionary. The
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