Python Learning notes (06)

Dictionary {}

tuple () list [] Dictionary {}       

Dictionary is the only mapping type (hash table) in Python

The Dictionary object is mutable, but the key of the dictionary must use the immutable object, and a dictionary can use different key values

Keys () or values () returns a list of key or value

Items () returns a tuple containing key-value pairs

How to define:

dic={' name ': ' SQL ', ' age ': +, ' gender ': ' Male '}

Value:

>>>dic[' name ']

Sql

>>>dic[age]

30

Note: Key can be a variable, or it can be a string

Access updates directly with key values; The built-in update () method can copy the entire content into another dictionary

Add a value

dict1[' tel ']= ' 123456 ' * added after position unordered

Modify a value

dict1[' tel ']= ' 234569 '

Update and delete

Del dict1[' A '] removes the element with a key value of a in the dictionary

· Dict1.pop (' a ') deletes and returns the element with the key ' a '

· Dict1.clear () Delete all elements of a dictionary

· Del (dict1) Delete entire dictionary

Len (), hash () is used to determine whether an object can do a dictionary key, non-hash type report TypeError error

Dict.clear () Delete all elements in the dictionary

Create and return a dictionary with the elements in Seq  , Val                                        defaults to default value

Dict.get (Key,default=none) returns the value of key, if the key does not exist, returns the values specified by default

Example: ss={' a ': 123, ' B ': 456}

Ss.get (A,error)

>>>123

Ss.get (' C ', error)

>>>error

Dict.has_key (key) to determine if a key exists in the dictionary, it is recommended to use in or not

Dict.items () Returns a list of key-value pairs of tuples

Dict.keys () returns the list of keys in the dictionary

dict.iter* () iteriterms (), Iterkeys (), itervalues () returns the iteration instead of the list

same as Get (), the difference is if key exists, delete and return                               Dict[key], if there is no tangent default value not specified , throw Keyerror exception

with Set (), if key is present, return to its                                                    value, if it does not exist Dict[key] =default

add the key-value pairs in dict2 to the dictionary dict if                                       Add

Dict.values () Returns a list of all values in the dictionary

This article is from the "Ride a Pig to Travel" blog, please be sure to keep this source http://songqinglong.blog.51cto.com/7591177/1710006

Python Learning notes (06)