The 11-day Python Learning record 2

Data Type-Dictionary

A dictionary is a Key-value data type, used as a dictionary of our school, to check the details of the corresponding page by strokes and letters.

Characteristics:

Key-value structure

Key must be hash, must be immutable data type, must be unique

can store any number of values, can be modified, can not be unique

Disordered

Fast Search Speed

Query Info.get () without this key will not error, info[] Without this key, will error, keyerror

Info.values () Remove value

Info.keys () Remove the key value

Info.setdefault () If there is this key, the value of this key is returned, and if there is no key, the dictionary is added

Info.update (b), add the Key-value in dictionary b to the info dictionary, if there is a duplicate key, then overwrite the key value, if there is no repetition, join

Info.items () produces a list of dictionary elements

Info.fromkeys () Generate default dict from a list, there's a pit that can't be explained, try to use less

Multilevel nesting of dictionaries

There are two types of loops:

1.for Key in Info:

Print (Key,info[key])

This method is simple, quick, and often used

2.for k,v in Info.items ():

Print (K,V)

This method will first convert the dictionary into a list, and then loop, execution efficiency is not the first method of high,

The 11-day Python Learning record 2