Python study notes Day 6 ‘Dictionaries’
On day six we will touch on something called dictionaries. In dictionary writing, a key corresponds to a value, and the order of the keys in the dictionary is not important.
variable = { key : value, key : value, key : value}
![Screen Shot 1](https://img-blog.csdnimg.cn/0ca32ae39f4c487287e77dc255447c8e.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
print(d)
![Screen Shot 2](https://img-blog.csdnimg.cn/ee5470daecd14606bf7e533f8e94b1fc.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
print(d)
print(d['a'])
![Screen Shot 3](https://img-blog.csdnimg.cn/c7feee9e0a2b4025811f9d63cafa0029.png)
dict = {'a' : (1,2), 'b' : [1,2], 'c' : {'aa' : 1, 'bb' : 2}}
print(dict)
print(dict['c']['aa'])
When we want to modify the value of a key in the dictionary: ![Screen Shot 4](https://img-blog.csdnimg.cn/418c9976fcc542888996f8cbd84e5809.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
d['a'] = 10
print(d)
When we want to add a key to the dictionary: ![Screen Shot 5](https://img-blog.csdnimg.cn/fd06b16671cd4c77a433bbc7bfe575c1.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
d['d'] = 4
print(d)
Note: Dictionaries are non-sequential containers When we want to delete a key from the dictionary: ![Screen Shot 6](https://img-blog.csdnimg.cn/dc0d688066a54f739e639bd33ba12789.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
del d['a']
print(d)
When we want to iterate through the elements in the dictionary(key:value): ![Screen Shot 7](https://img-blog.csdnimg.cn/607c1d1a23cc4fddb313f343af508df8.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
for key,value in d.items():
print('key:',key,'\t','value',value)
When we want to iterate through the elements in the dictionary(key): ![Screen Shot 8](https://img-blog.csdnimg.cn/8d14604a44aa4833835a9a8bdec3cffb.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
for key in d.keys():
print('key:',key)
(value): ![Screen Shot 9](https://img-blog.csdnimg.cn/12ad7019d0334a479d77762eb2b0f429.png)
d = {'a' : 1, 'b' : 2, 'c' : 3}
for value in d.values():
print('value:',value)
![Screen Shot 10](https://img-blog.csdnimg.cn/24ec5ffe76334e75a8af78364b600b14.png)
d = {'a' : 1, 'b' : 6, 'c' : 3}
for value in sorted(d.values()):
print('value:',value)
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