Dictionaries in Python
I. Characteristics of dictionaries
II. Creating Dictionaries
Creating a dictionary is indicated by curly brackets
dict1={'a':3,'b':4,'c':7} ## The first way to create
print(dict1)
dict2=dict(a=2,b=3) ## The first way to create
print(dict2)
{'a': 3, 'b': 4, 'c': 7}
{'a': 2, 'b': 3}
III. Querying dictionary data
dict2=dict(a=2,b=3) ## Create a dictionary
print(dict2['a']) ## Look up the value of a in the dictionary and throw an exception if the key does not exist.
print(('a')) ## Make the get method look up the value of a in the dictionary, and return none if the key doesn't exist.
2
2
IV. Key's judgment
dict2=dict(a=2,b=3) print( 'a' in dict2) print( 'a' not in dict2) True False
V. Deletion of Keys
dict2=dict(a=2,b=3) ## Delete, clear as clear
del dict2['a']
print(dict2)
{'b': 3}
VI. Adding Keys
dict2=dict(a=2,b=3) ##
dict2['c']=4
print( dict2 )
{'a': 2, 'b': 3, 'c': 4}
VII. Modification of Key
dict2=dict(a=2,b=3) ## The first way to create
dict2['c']=4 ##Add c with a value of 4
print( dict2 )
dict2['c']=10 ##Modify the value of c to 10
print( dict2 )
{'a': 2, 'b': 3, 'c': 4}
{'a': 2, 'b': 3, 'c': 10} ##c has been changed to 10
VIII. Dictionary views
keys()
Get all the keys in the dictionary
test={'Zhang San':56,'Li Si':56}
print(())
print(list(()) ## Convert to list
dict_keys(['Zhang San', 'Li Si'])
['Zhang San', 'Li Si']
values()
Get all values in the dictionary
values=() print(values) dict_values([56, 56]) [56, 56]
iterms()
Get all pairs of keys and values in the dictionary.
iterm=()
print(iterm)
print(list(iterm)) ## The list element after conversion is a set of meta-ancestors
dict_items([('Zhang San', 56), ('Li Si', 56)])
[('Zhang San', 56), ('Li Si', 56)]
IX. Iteration of the dictionary
dic1={'a':2,'b':3,'c':4}
for i in dic1:
print(i) ## Iterate over the key of the dictionary
print((i)) ## Printing values using the get function
print(dic1[i]) ## The second way to traverse values
X. Expressions for generating dictionaries
name=['Zhang San','Li Si','Wang Wu']
age=[23,45,37]
d= {name:age for name,age in zip(name,age)} #Note the extra parentheses at the top
print(d)
```
d= {test:age for test,age in zip(name,age)} ## has nothing to do with the variable name, zip packed values do
print(d) ## Same result
```
{'Zhang San': 23, 'Li Si': 45, 'Wang Wu': 37}
Brackets should be added to the outside.
print(d)
```
d= {test:age for test,age in zip(name,age)} ## has nothing to do with the variable name, zip packed values do
print(d) ## Same result
```
{'Zhang San': 23, 'Li Si': 45, 'Wang Wu': 37}
summarize
That's all for this post, I hope it was helpful and I hope you'll check back for more from me!