A Dictionary of Python

I. Introduction to the Dictionary

1. A dictionary is another mutable container model and can store any type of object.

2. Each key value of the dictionary key-value pairs with a colon : Split, each key-value pair is separated by commas, and the entire dictionary is included in the curly braces {}, as shown in the following format:D = { key1 : value1, key2 : value2 }

3. The dictionary is unordered

4. The key in the dictionary is unique, if key is already present, overwrite the value of key, and if key does not exist, insert a key value pair

5. The value can take any data type, but the key must be immutable, such as a string, a number, or a tuple

Second, the use of the dictionary

data = {' name ': ' Zhang San ',

' Age ': 18,

' Sex ': ' Woman '}

1. Increase

data[' email ']= ' [email protected] '

Data.setdefault (' age ', $) #setdefault这种方式, if key already exists, regardless of it, if key does not exist, add

2. Modifications

data[' sex ']= ' man '

3. Delete

Data.pop (' sex ') #指定的key来删除, key does not exist will error

del data[' sex '] #指定的key来删除, key does not exist will error

4. Take the value

data[' sex ']

Data.get (' sex1 ', ' haha ') #返回指定键的值 if the value does not return the default value in the dictionary (' haha ')

5. Other

Data.clear () #清空字典

Data.update (DATA2) #把字典2的键值对加入到字典里

Data.items () #以列表返回可遍历的 (key, value) tuple array

Data.keys () #以列表返回一个字典所有的键

Data.valus #以列表返回一个字典所有的值

Data.popitem () #随机返回并删除字典中的一对键和值

6. How to efficiently cycle a dictionary:

For k in data:

Print (K,data.get (k))

　

A Dictionary of Python