{"id":1846,"date":"2020-07-21T09:58:24","date_gmt":"2020-07-21T04:28:24","guid":{"rendered":"https:\/\/copyassignment.com\/?page_id=1846"},"modified":"2022-10-22T17:13:10","modified_gmt":"2022-10-22T11:43:10","slug":"python-dictionary","status":"publish","type":"page","link":"https:\/\/copyassignment.com\/python\/python-dictionary\/","title":{"rendered":"Python Dictionary"},"content":{"rendered":"\n

Definition<\/h2>\n\n\n\n

A Python dictionary<\/a> is a collection of \"key\"<\/strong><\/code>and\"value\"<\/strong><\/code>pairs.<\/p>\n\n\n\n

Dictionaries are \"unordered\"<\/strong><\/code>, \"indexed\"<\/strong><\/code>, \"mutable\"<\/strong><\/code> i.e. can be changed after their creation, and are enclosed with \"curly brackets {}\"<\/strong><\/code>.<\/p>\n\n\n\n

These are \"mapping\"<\/strong><\/code> type data-type in Python.<\/p>\n\n\n\n

Keys and values are separated by \"colon(:)\"<\/strong><\/code> and key-value pairs are separated using \"comma(,)\"<\/strong><\/code>.<\/p>\n\n\n\n

Keys<\/h3>\n\n\n\n

Keys can be a \"single element\"<\/strong><\/code> only and should be immutable Python objects i.e. \"numbers\"<\/strong><\/code>, \"strings\"<\/strong><\/code>, and \"tuples\"<\/strong><\/code>.<\/p>\n\n\n\n

Values<\/h3>\n\n\n\n

A value in a dictionary can be any Python object like \"list\"<\/strong><\/code>, \"tuple\"<\/strong><\/code>, \"number\"<\/strong><\/code>, \"string\"<\/strong><\/code>, and even the \"dictionary\"<\/strong><\/code>.<\/p>\n\n\n\n

Creating a Dictionary<\/h2>\n\n\n\n

Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nprint(type(mydict))<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n<class 'dict'><\/pre><\/div>\n\n\n\n
dict() method<\/h2>\n\n\n\n
We can also use \"dict()\"<\/strong><\/code>method to create a dictionary.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
myDict = dict(key1=\"value1\", key2=\"value2\",key3=\"value3\")\nprint(type(myDict))\nprint(myDict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
<class 'dict'>\n{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}<\/pre><\/div>\n\n\n\n
Accessing values<\/h2>\n\n\n\n
We can access dictionary values using a \"key name\"<\/strong><\/code> or using \"get()\"<\/strong><\/code> method.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nprint(mydict[\"key1\"])\nprint(mydict.get(\"key2\"))<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\nValue1\nValue2<\/pre><\/div>\n\n\n\n
Updating Dictionary<\/h2>\n\n\n\n
We can add more key-value pairs in a dictionary, change the value of a key, and can also take value from the user at run time.<\/p>\n\n\n\n
Use \"dictname[keyname] = value\"<\/strong><\/code> to add or change a key-value pair.<\/p>\n\n\n\n
If the keyname does not exist then a new key-value pair will be created and added to the dictionary else the value of the key will be changed.<\/p>\n\n\n\n
We can also take a key’s value from the user at run time of the Python code using \"input()\"<\/strong><\/code>function.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nmydict[\"newkey1\"] = \"newvalue1\"\nmydict[\"key1\"] = \"updatedvalue1\"\nprint(mydict)\nmydict[\"userinput\"] = input(\"Enter value: \")\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'updatedvalue1', 'key2': 'Value2', 'key3': 'Value3', 'newkey1': 'newvalue1'}\nEnter value: myinputvalue\n{'key1': 'updatedvalue1', 'key2': 'Value2', 'key3': 'Value3', 'newkey1': 'newvalue1', 'userinput': 'myinputvalue'}<\/pre><\/div>\n\n\n\n
We can also use \"update()\"<\/strong><\/code> method to add many key-value pairs at one time.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nmydict.update({\"key4\":\"value4\", \"key5\":\"value5\", \"key6\":\"value6\"})\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3', 'key4': 'value4', 'key5': 'value5', 'key6': 'value6'}<\/pre><\/div>\n\n\n\n
Dictionary Length<\/h2>\n\n\n\n
We can determine the number of key-value pairs using \"len()\"<\/strong><\/code> method.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(len(mydict))<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
3<\/pre><\/div>\n\n\n\n
Checking a Key in Dictionary<\/h2>\n\n\n\n
We can check whether a key-value pair exists in a dictionary using in keyword \"in\"<\/strong><\/code> Python.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(\"key1\" in mydict)\nprint(\"key2\" in mydict)\nprint(\"key5\" in mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
True\nTrue\nFalse<\/pre><\/div>\n\n\n\n
del keyword<\/h2>\n\n\n\n
Use \"del\"<\/strong><\/code> keyword to delete a key-value pair in a dictionary.<\/p>\n\n\n\n
Syntax–<\/strong> del dictname[\"keyname\"]<\/strong><\/code><\/p>\n\n\n\n
Note–<\/strong> this keyword can also be used to delete the entire dictionary.<\/p>\n\n\n\n
Syntax–<\/strong> del dictname<\/strong><\/code><\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\ndel mydict[\"key1\"]\nprint(mydict)\ndel mydict\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key2': 'Value2', 'key3': 'Value3'}\nTraceback (most recent call last):\n  File \"f:\/vscode\/python\/dicttutorial.py\", line 10, in <module>\n    print(mydict)\nNameError: name 'mydict' is not defined<\/pre><\/div>\n\n\n\n
pop() method<\/h2>\n\n\n\n
We can also use \"pop()\"<\/strong><\/code> method to remove any key-value pair using the specified key name.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nmydict.pop(\"key1\")\nprint(mydict)\nmydict.pop(\"key2\")\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key2': 'Value2', 'key3': 'Value3'}\n{'key3': 'Value3'}<\/pre><\/div>\n\n\n\n
popitem() method<\/h2>\n\n\n\n
This method simply removes the last key-value pair present in the dictionary.<\/p>\n\n\n\n
Note–<\/strong> In versions before 3.7, it was used to remove a random key-value pair.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nmydict.popitem()\nprint(mydict)\nmydict.popitem()\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'Value1', 'key2': 'Value2'}\n{'key1': 'Value1'}<\/pre><\/div>\n\n\n\n
clear() method<\/h2>\n\n\n\n
If we want to make our dictionary completely empty then we can use this method.<\/p>\n\n\n\n
This method will remove all the key-value pairs from the dictionary but the name of the dictionary will be available as it was before.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nprint(mydict)\nmydict.clear()\nprint(mydict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{}<\/pre><\/div>\n\n\n\n
Copy a Dictionary<\/h2>\n\n\n\n
We can directly assign a dictionary to any variable using the assignment operator\"(=)\"<\/strong><\/code>.<\/p>\n\n\n\n
 But this will not be called as copying a dictionary because here we are only referring to the old dictionary using the assignment operator like we simply assign some value to any variable\"a = 5\"<\/strong><\/code>. <\/p>\n\n\n\n
So, if we make any changes in the previous dictionary, then we will see those changes in our new copied dictionary.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nnewdict = mydict\nprint(mydict)\nprint(newdict)\nmydict[\"key1\"] = \"newvalue\"\nprint(mydict)\nprint(newdict)<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'newvalue', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'newvalue', 'key2': 'Value2', 'key3': 'Value3'}<\/pre><\/div>\n\n\n\n
Use \"copy()\"<\/strong><\/code> method if you want to create a new copied dictionary.<\/p>\n\n\n\n
Example<\/h3>\n\n\n\n
<\/span><\/div>
mydict = {\n    \"key1\" : \"Value1\",\n    \"key2\" : \"Value2\",\n    \"key3\" : \"Value3\"\n}\nnewdict = mydict.copy()\nprint(newdict)\nmydict[\"key1\"] = \"newvalue\"\nprint(mydict)\nprint(newdict) # newdict will not be effected<\/pre><\/div>\n\n\n\n
Output<\/h3>\n\n\n\n
{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'newvalue', 'key2': 'Value2', 'key3': 'Value3'}\n{'key1': 'Value1', 'key2': 'Value2', 'key3': 'Value3'}<\/pre><\/div>\n\n\n\n
\n
Previous– Python Sets<\/a><\/div>\n\n\n\n
Next– Python Operators<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
Definition A Python dictionary is a collection of “key”and”value”pairs. Dictionaries are “unordered”, “indexed”, “mutable” i.e. can be changed after their creation, and are enclosed with…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":833,"menu_order":12,"comment_status":"closed","ping_status":"closed","template":"template-s1-c-page.php","meta":{"footnotes":""},"class_list":["post-1846","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/pages\/1846","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/comments?post=1846"}],"version-history":[{"count":0,"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/pages\/1846\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/pages\/833"}],"wp:attachment":[{"href":"https:\/\/copyassignment.com\/wp-json\/wp\/v2\/media?parent=1846"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}