Learning Python-Basic course: Day 18, Dictionaries in Python

Learning Python (72 Part Series)

Welcome all🤟 Today we will cover dictionaries!

Dictionary is simply a collection of unordered key value pairs
Or sometimes referred as a ‘hash table’ of key value pairs. Dictionary holds key:value pair. this means that every value in an dictionary is mapped with some other value. Values in a dictionary can be of any datatype. Dictionaries cannot have two items with the same key for obvious reasons.
example

AatmajProfileDictionary={"name":"Aatmaj","Hobby":"teaching","Commits":700}

Enter fullscreen mode Exit fullscreen mode

Here is a quick difference between lists, tuples and dictionaries.

a=[] #list a=() #tuple a={}#dictionary

Enter fullscreen mode Exit fullscreen mode

Hash table

A Hash table is a data structure. A hash table is a data structure that implements an associative array abstract data type that can map keys to values. A hash table uses a hash function to compute an index also called as the hash code, into a array of buckets or slots, from which the desired value can be found.

As of Python version 3.7, dictionaries are ordered. In Python 3.6 and earlier, dictionaries are unordered.

Sample program-

Here is a sample program just to get you started with dictionaries. It is quite easy to understand and commented whenever necessary

>>> hardware={    "Brand": "Dell",    "Model": 2430,    "Year":  "2020"}
>>> print(hardware) #prints the value of the dictionary {'Brand': 'Dell', 'Model': 2430, 'Year': '2020'}
>>> print(hardware["Model"])
2430
>>> print(hardware.get("Model"))
2430
>>> hardware["Year"]=2021 #Changing the value of the dictionary >>> print(hardware)
{'Brand': 'Dell', 'Model': 2430, 'Year': 2021}
>>> print(hardware.pop("Model"))
2430
>>> print(hardware)
{'Brand': 'Dell', 'Year': 2021}
>>> hardware["Model"]="Lenovo"
>>> hardware["Year"]=2019
>>> print(hardware.popitem()) #popitem returns the last value entered ('Model', 'Lenovo')
>>> print(hardware)
{'Brand': 'Dell', 'Year': 2019}
>>> for y in hardware:
...     print(y)#Corresponds to each key ...
Brand
Year
>>> for x in hardware:
...      print(hardware[x])#refers to the value ...
Dell
2019
>>> for z in hardware.values():
...      print(z)
...
Dell
2019
>>> hardware.clear() #Cleares the dictionary (not delete) >>> print(hardware)
{}
>>> print(hardware["Price"])#trying to remove element which is not present Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'Price'

Enter fullscreen mode Exit fullscreen mode

Multidimensional dictionaries

Same story needs no explanation!

hardware={
    "LAPTOP":{"Brand": "Dell","Model": 2430,"Year":  "2020"},
    "DESKTOP":{"Brand":"Lenovo","Model":8877,"Warranty": 2},
    "TABLET":{"Brand":"Apple", "price":"3000$"}
}
print(hardware)
print(hardware["TABLET"])
print(hardware["LAPTOP"]["Model"]) #Note the syntax

Enter fullscreen mode Exit fullscreen mode

{'TABLET': {'price': '3000$', 'Brand': 'Apple'}, 'LAPTOP': {'Model': 2430, 'Brand': 'Dell', 'Year': '2020'}, 'DESKTOP': {'Model': 8877, 'Brand': 'Lenovo', 'Warranty': 2}}
{'price': '3000$', 'Brand': 'Apple'}
2430

Enter fullscreen mode Exit fullscreen mode

Exercise-
1) Make a dictionary which contains a list and a tuple. Then append the tuple in the list in the dictionary.

2) Dynamic generation of dictionaries– Write a program to take names of five students and their corresponding marks, put them in an dictionary.
output-

Please enter student name peter
Please enter marks 13
Please enter student name john
Please enter marks 32
Please enter student name pappu
Please enter marks 5
Please enter student name bob
Please enter marks 7
Please enter student name mina
Please enter marks 32
{'peter': 13, 'john': 32, 'pappu': 5, 'mina': 32, 'bob': 7}

Enter fullscreen mode Exit fullscreen mode

Answers will be found here

So friends that’s all for this part. For any suggestions please ping me🤠.
Here is my Gmail- aatmaj.mhatre@gmail.com 🤟
Don’t forget to follow me on GitHub for updates on the course.

Learning Python (72 Part Series)

原文链接：Learning Python-Basic course: Day 18, Dictionaries in Python

文章版权声明 1、本网站名称：拾光赋
2、本站永久网址：https://www.blogs.ink
3、本网站的文章部分内容可能来源于网络，仅供大家学习与参考，如有侵权，请联系站长QQ：805375623进行删除处理。
4、本站一切资源不代表本站立场，并不代表本站赞同其观点和对其真实性负责。
5、本站一律禁止以任何方式发布或转载任何违法的相关信息，访客发现请向站长举报
6、本站资源大多存储在云盘，如发现链接失效，请联系我们我们会第一时间更新。

THE END