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Today, I would like to share with you the relevant knowledge points about the skills of using Python dictionary. The content is detailed and the logic is clear. I believe most people still know too much about this, so share this article for your reference. I hope you can get something after reading this article. Let's take a look at it.

Dictionary (Dictionary) is a commonly used data structure provided by Python. It is used to store mapped data. It consists of key and value pairs. Keys and values are separated by colons, items are separated by commas, and the whole dictionary is enclosed by braces {}. The format is as follows:

Dic = {key1: value1, key2: value2}

Dictionaries are also called associative arrays or hash tables, and here are several common ways to create dictionaries:

# method 1dic1 = {'Author':' Python', 'age': 99,' sex': 'male'} # method 2lst = [('Author',' Python'), ('age', 99), (' sex', 'male')] dic2 = dict (lst) # method 3dic3 = dict (Author = 'Python', age = 99, sex =' male') # method 4list1 = ['Author',' age' 'sex'] list2 = [' Python', 99, 'male'] dic4 = dict (zip (list1, list2))

There are many other ways to create dictionaries, so I won't repeat them here.

The dictionary is represented by the dict class. You can use dir (dict) to see which methods the class contains. Enter the command and you can see the following output:

Print ('methods =', methods) methods = ['_ _ class__','_ _ contains__','_ _ delattr__','_ _ delitem__','_ _ dir__','_ _ doc__','_ _ eq__','_ _ format__','_ ge__','_ getattribute__','_ getitem__','_ _ gt__','_ _ hash__' '_ _ init__',' _ _ init_subclass__','_ _ iter__','_ _ le__','_ _ len__','_ _ lt__','_ _ ne__','_ _ new__','_ _ reduce__','_ _ reduce_ex__','_ repr__','_ reversed__','_ setattr__','_ _ setitem__' '_ _ sizeof__',' _ _ str__','_ _ subclasshook__', 'clear',' copy', 'fromkeys',' get', 'items',' keys', 'pop',' popitem', 'setdefault',' update', 'values']

There are many methods and properties for dictionaries. Here we focus on the following 11 methods:

['clear',' copy', 'fromkeys',' get', 'items',' keys', 'pop',' popitem', 'setdefault',' update', 'values'] 1.dict.clear ()

Clear () is used to empty all elements (key-value pairs) in the dictionary, and after executing the clear () method on a dictionary, the dictionary becomes an empty dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', 99, 'male'] dic1 = dict (zip (list1, list2)) # dic1 = {'Author':' Python', 'age': 99,' sex': 'male'} dic1.clear () # dic1 = {} 2.dict.copy ()

Copy () is used to return a shallow copy of a dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', 99, 'male'] dic1 = dict (zip (list1, list2)) dic2 = dic1 # shallow copy: reference object dic3 = dic1.copy () # shallow copy: deep copy parent object (primary directory), child object (secondary directory) is not copied Also quote dic1 ['age'] =' Author': 'Python',' age': 18, 'sex':' male'} # dic2 = {'Author':' Python', 'age': 18,' sex': 'male'} # dic3 = {'Author':' Python', 'age': 99,' sex': 'male'}

Where dic2 is a reference to dic1, so the output result is consistent. The parent object of dic3 is deeply copied and will not be modified with the modification of dic1. The child object is a shallow copy, so it is modified with the modification of dic1. Pay attention to the parent-child relationship.

Extended deep copy: copy.deepcopy ()

Import copylist1 = ['Author',' age', 'sex'] list2 = [' Python', [18PC99], 'male'] dic1 = dict (zip (list1, list2)) dic2 = dic1dic3 = dic1.copy () dic4 = copy.deepcopy (dic1) dic1 ['age'] .remove (18) dic1 [' age'] = 2percent dic1 = {'Author':' Python', 'age': 20,' sex': 'male'} # dic2 = {'Author':' Python', 'age': 20 'sex':' male'} # dic3 = {'Author':' Python', 'age': [99],' sex': 'male'} # dic4 = {'Author':' Python', 'age': [18,99],' sex': 'male'}

Dic2 is a reference to dic1, so the output is consistent; dic3 parent object is deeply copied and will not be modified with dic1 modification, while child object is shallow copy, so it is modified with dic1 modification; dic4 makes deep copy and recursively copies all data, which is equivalent to completely creating the original dictionary in another memory, so modifying dic1 will not affect dic4 data.

3.dict.fromkeys ()

Fromkeys () creates a new dictionary with multiple keys given. The default value is None, or you can pass in a parameter as the default value:

List1 = ['Author',' age', 'sex'] dic1 = dict.fromkeys (list1) dic2 = dict.fromkeys (list1,' Python') # dic1 = {'Author': None,' age': None, 'sex': None} # dic2 = {' Author': 'Python',' age': 'Python',' sex': 'Python'} 4.dict.get ()

Get () is used to return the value of the specified key, that is, to get the value based on the key, or to return None if the key does not exist, or you can specify the return value:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [18Power99], 'male'] dic1 = dict (zip (list1, list2)) Author = dic1.get ('Author') # Author = Pythonphone = dic1.get (' phone') # phone = Nonephone = dic1.get ('phone','12345678') # phone = 123456785.dict.items ()

Items () gets all the key-value pairs in the dictionary, and in general, you can convert the result to a list for subsequent processing:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [18d99], 'male'] dic1 = dict (zip (list1, list2)) items = dic1.items () print ('items =', items) print (type (items)) print ('items =', list (items)) # items = dict_items ([('Author',' Python'), ('age', [18599]), (' sex') ) # # items = [('Author',' Python'), ('age', [18,99]), (' sex', 'male')] 6.dict.keys ()

Keys () returns all the keys in a dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [18PC99], 'male'] dic1 = dict (zip (list1, list2)) keys = dic1.keys () print ('keys =', keys) print (type (keys)) print ('keys =', list (keys)) # keys = dict_keys ([Author', 'age',' sex']) # # keys = ['Author',' age', 'sex'] 7.dict.pop ()

Pop () returns the value corresponding to the specified key and deletes the key-value pair from the original dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [18LC99], 'male'] dic1 = dict (zip (list1, list2)) sex = dic1.pop ('sex') print (' sex =', sex) print ('dic1 =', dic1) # sex = male # dic1 = {'Author':' Python', 'age': [185,99]} 8.dict.popitem ()

Popitem () deletes the last pair of keys and values in the dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [18Power99], 'male'] dic1 = dict (zip (list1, list2)) dic1.popitem () print ('dic1 =', dic1) # dic1 = {'Author':' Python', 'age': [18jue 99]} 9.dict.setdefault ()

Setdefault () is similar to get (), but if the key does not exist in the dictionary, the key is added and the value is set to default:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [181499], 'male'] dic1 = dict (zip (list1, list2)) dic1.setdefault ('Author','') print ('dic1 =', dic1) # dic1 = {'Author':' Python', 'age': [18jur99],' sex': 'male'} dic1.setdefault ('name',') print ('dic1 =' Dic1) # dic1 = {'Author':' Python', 'age': [18,99],' sex': 'male', 'name':'} 10.dict.update (dict1)

Update the update () dictionary to update the key-value pair of the dictionary dict1 to dict. If the updated dictionary already contains the corresponding key-value pair, then the original key-value pair will be overwritten. If the updated dictionary does not contain the corresponding key-value pair, the key-value pair will be added:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [1899], 'male'] dic1 = dict (zip (list1, list2)) print ('dic1 =', dic1) # dic1 = {'Author':' Python', 'age': [1899],' sex': 'male} list3 = [' Author', 'phone'] list4 = [', 12345678] dic2 = dict (zip (list3, list4)) print ('dic2 =') Dic2) # dic2 = {'Author':'', 'phone': 12345678} dic1.update (dic2) print (' dic1 =', dic1) # dic1 = {'Author':'', 'age': [18,99],' sex': 'male', 'phone': 12345678} 11.dict.values ()

Values () returns all the values of a dictionary:

List1 = ['Author',' age', 'sex'] list2 = [' Python', [1899], 'male'] dic1 = dict (zip (list1, list2)) values = dic1.values () print ('values =', values) print (type (values)) print ('values =', list (values)) # values = dict_values (['Python', [188,99],' male']) # # values = ['Python', [1899] The above is all the content of the article "what are the tips for using Python dictionaries?" Thank you for reading! I believe you will gain a lot after reading this article. The editor will update different knowledge for you every day. If you want to learn more knowledge, please pay attention to the industry information channel.

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