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Installation and use

Installation

Install the redis module

Pip3 install redis normal connection

Redis-py provides two classes, Redis and StrictRedis, to implement commands for Redis. StrictRedis is used to implement most official commands and uses official syntax and commands. Redis is a subclass of StrictRedis and is used for backward compatibility with older versions of redis-py

Import redisconn = redis.Redis (host='127.0.0.1', port=6379) # you can use url to connect to the database # conn = Redis.from_url ('redis://@localhost:6379/1') conn.set (' name', 'LinWOW') print (conn.get (' name')) connection pool

Redis-py uses connection pool to manage all connections to a redis server, avoiding the overhead of establishing and releasing connections each time. By default, each Redis instance maintains its own connection pool. You can directly establish a connection pool and then use it as a parameter Redis, so that multiple Redis instances can share a connection pool.

Connection pooling: redis_pool.py

From redis import ConnectionPoolPOOL=ConnectionPool (host='127.0.0.1',port=6379,max_connections=100)

Use connection Pool: test_redis.py

Import redisfrom redis_pool import POOlconn = redis.Redis (connection_pool=POOl) conn.set ('name',' LinWOW') print (conn.get ('name'))

There are three modes to connect to the database in the way of constructing url:

Redis:// [: password] @ host:port/db # TCP connection rediss:// [: password] @ host:port/db # Redis TCP+SSL connection unix:// [: password] @ / path/to/socket.sock?db=db # Redis Unix Socket connection Python operation RedisString operation example result set (name, value, ex=None, px=None, nx=False, xx=False) ex, expiration time (s); px, expiration time (ms) Nx, if set to True, the current set operation is executed only when name does not exist. If the value exists, it cannot be modified, and the execution has no effect; xx, if set to True, the current set operation is executed only when name exists, and the value can be modified only if the value exists, but the value does not exist, and the new value effect will not be set to be consistent with setex,setnx.

Set (name, value) assigns name a value of valueredis.set ('name',' Bob') Trueget (name) returns valueredis.get ('name') b'Bob'getset (name, value) of string with key of name in the database, assigns the value value of string of key to name in the database and returns the last valueredis.getset (' name', 'Mike') b'Bob'mget (keys, * args) returning multiple valueredis.mget ([' name', 'nickname']) [baked mix') corresponding to key. Baked Miker'] setnx (name, value) set valueredis.setnx ('newname',' James') to run True for the first time if key does not exist The second Falsesetex (name, time, value) setting can correspond to a value of type string, and specify the validity period corresponding to this key value redis.setex ('name', 1,' James') Truesetrange (name, offset, value) set the substring redis.set ('name',' Hello') redis.setrange ('name', 6,' World') 11 of the value of the specified key When the modified string length mset (mapping) batch assignment redis.mset ({'name1':' Durant', 'name2':' James'}) Truemsetnx (mapping) key does not exist, then the batch assignment redis.msetnx ({'name3':' Smith', 'name4':' Curry'}) Trueincr (name, amount=1) key is the value value-added operation of name. If the default key does not exist, it is created and set to amountredis.incr ('age', 1) 1. That is, the modified value decr (name, amount=1) key is the value impairment operation of name, and if the default 1 age', key does not exist, it is created and set to-amountredis.decr ('age', 1)-1, that is, the modified value append (key, value) key is the string value of name plus valueredis.append (' nickname', 'OK') 13 That is, the modified string length substr (name, start, end=-1) returns the substring redis.substr ('name', 1,4) b'ello'getrange (key, start, end) of string whose key is name. Get the value of key from start to the substring redis.getrange (' name', 1) of end 4) b'ello'Key operation method action example result exists (name) determines whether a key exists redis.exists ('name') Truedelete (name) deletes a keyredis.delete (' name') 1type (name) determines the key type redis.type ('name') b'string'keys (pattern) gets all the rules-compliant keyredis.keys (' 1type') randomkey () gets a random keyrandomkey () b'name'rename (src) Dst) rename key redis.rename ('name',' nickname') Truedbsize () get the number of key in the current database dbsize () 100expire (name, time) set the expiration time of key Unit second redis.expire ('name', 2) Truettl (name) gets the expiration time of key, in second -1 for permanent non-expired redis.ttl ('name')-1move (name, db) move key to another database move (' name', 2) Trueflushdb () Delete all keyflushdb () Trueflushall () in the currently selected database delete all keyflushall () TrueList operation method in all databases example result rpush (name, * values) add an element with the value value at the end of the list whose key is name You can pass multiple redis.rpush ('list', 1,2,3) 3 lpush (name, * values) add an element with a value of value to the list header of key for name, and you can pass multiple redis.lpush (' list', 0) 4 List size llen (name) returns the length of the list whose key is name redis.llen ('list') 4lrange (name, start, end) returns the element redis.lrange (' list', 1,3) between start and end in the list where key is name. [baked 3, baked 2, bounded 1'] ltrim (name, start, end) intercepts list with key as name Content ltrim ('list', 1,3) Truelindex (name, index) with an index of start to end returns the element redis.lindex (' list', 1) b'2'lset (name, index, value) with the position of index in the list of name as key assigns a value to the element of index position in list where key is name. If it crosses the boundary, it reports an error redis.lset ('list', 1,5) Truelrem (name, count, value) to delete redis.lrem (' list', 2,3) 1 of count key's list which has the value of value. That is, the number of deleted lpop (name) returns and deletes the first element redis.lpop ('list') b'5'rpop (name) in the list whose key is name, returns and deletes the tail element redis.rpop (' list') b'2'blpop (keys, timeout=0) in the list whose key is name, and deletes the first element in the list whose name is keys, if list is empty It will always block waiting for redis.blpop ('list') [bread5'] brpop (keys, timeout=0) to return and delete the tail element in the list whose key is name. If list is empty, it will block waiting for redis.brpop (' list') [bread2'] rpoplpush (src, dst) to return and delete the tail element of list named src and add the element to the header redis.rpoplpush ('list',' list2') bread2' of list named dst

Application scenarios:

Blpop implements a simple distributed crawler:

Multiple url are put into the list, URL is not stopped in the list, and the program takes values in a loop, but only one machine can run the values. You can put url into redis, and multiple machines take values from redis and crawl data to achieve simple distribution.

Arrange multiple lists according to the elements that pop the corresponding list from left to right

Parameters:

Collection of name for keys,redis

Timeout, timeout. When all the list elements of the element have been fetched, the blocking waits for the time in which there is data in the list (in seconds). 0 means forever blocking.

More:

R.brpop (keys, timeout) to get data from right to left

Custom incremental iterations:

Since incremental iterations over list elements are not provided in the redis class library, if you want to loop through all the elements of the list corresponding to name, you need to:

1. Get all the lists corresponding to name

2. Circular list

However, if the list is very large, it is possible to burst the contents of the program in the first step, so it is necessary to customize the functionality of an incremental iteration:

Import redisconn=redis.Redis (host='127.0.0.1',port=6379) # conn.lpush ('test',*] # conn.flushall () def scan_list (name,count=2): index=0 while True: data_list=conn.lrange (name,index) Count+index-1) if not data_list: return index+=count for item in data_list: yield itemprint (conn.lrange ('test',0100)) for item in scan_list (' test',5): print ('-') print (item) Set Operation example result sadd (name, * values) add element redis.sadd ('tags',' Book') to set where key is name 'Tea',' Coffee') 3 That is, the number of data inserted srem (name, * values) deletes the element redis.srem ('tags',' Book') 1 from the set whose key is name. That is, the number of deleted data spop (name) randomly returns and deletes an element redis.spop ('tags') b'Tea'smove (src, dst, value) in the set whose key is name. Remove the element from the set corresponding to src and add it to the set corresponding to dst. Redis.smove (' tags', 'tags2',' Coffee') Truescard (name) returns the number of elements redis.scard ('tags') 3sismember (name) of set key as name Value) tests whether member is an element of set whose key is name redis.sismember ('tags',' Book') Truesinter (keys, * args) returns the intersection of set of all given key redis.sinter (['tags',' tags2']) {baked Coffee'} sinterstore (dest, keys, * args) and saves the intersection to dest's collection redis.sinterstore ('inttag', [' tags', 'tags2']) 1sunion (keys) * args) returns the union of set of all given key redis.sunion (['tags',' tags2']) {bounded Coffee, bounded Bookstore, bounded Pen'} sunionstore (dest, keys, * args) and saves the union to the collection of dest redis.sunionstore ('inttag', [' tags', 'tags2']) 3sdiff (keys, * args) returns the difference of set of all given key redis.sdiff ([' tags', 'tags2']) {baked Book' Bounded Pen'} sdiffstore (dest, keys, * args) takes the difference set and saves the difference set to the collection of dest redis.sdiffstore ('inttag', [' tags', 'tags2']) 3smembers (name) returns all elements of set whose key is name redis.smembers (' tags') {bounded Pennsylvania, baked Bookstores, bounded Coffee'} srandmember (name) randomly returns an element of set whose key is name But does not delete the element redis.srandmember ('tags')

The Sorted Set operation method works sample result zadd (name, args, * kwargs) adds the element member,score to the zset where key is name for sorting. If the element exists, update its order redis.zadd ('grade', 100,' Bob', 98, 'Mike') 2, that is, the number of elements added zrem (name, * values) deletes the element redis.zrem (' grade', 'Mike') 1 in the zset whose key is name, that is, the number of elements deleted zincrby (name, value, amount=1) if the element value already exists in the zset where key is name, the score of that element increases amount Otherwise, add the element to the collection, whose score value is amountredis.zincrby ('grade',' Bob',-2) That is, the modified value zrank (name, value) returns the ranking of elements in zset with key as name (sorted by score from smallest to largest), that is, the subscript redis.zrank ('grade',' Amy') 1zrevrank (name, value) returns the reciprocal ranking of elements in zset with key as name (sorted by score from largest to smallest), that is, subscript redis.zrevrank ('grade',' Amy') 2zrevrange (name, start, end) Withscores=False) returns all elements redis.zrevrange ('grade', 0,3) from start to end in zset with key of name (sorted by score from largest to smallest) [baked bobbles, baked mikes, baked Amyths, baked James'] zrangebyscore (name, min, max, start=None, num=None, withscores=False) returns elements redis.zrangebyscore ('grade', 80,95) of score in a given interval in zset where key is name [baked AMYONES, baked James'] zcount (name, min James') Max) returns the number of zset where key is name redis.zcount ('grade', 80,95) 2zcard (name) returns the number of elements of zset whose key is name redis.zcard (' grade') 3zremrangebyrank (name, min, max) deletes the element redis.zremrangebyrank ('grade', 0,0) 1 ranked in the given interval in zset where key is name That is, the number of deleted elements zremrangebyscore (name, min, max) deletes the element redis.zremrangebyscore ('grade', 80,90) 1 of zset where key is name, that is, the element redis.zremrangebyscore (' grade', 80,90) 1 of score in a given interval, that is, the number of deleted elements Hash operation method works example result hset (name, key, value) adds mapping hset ('price',' cake', 5) 1 to hash where key is name, that is, the number of mappings hsetnx (name, key, value) adds mapping to hash where key is name If the mapping key name does not exist hsetnx ('price',' book', 6) 1 That is, the number of added mappings hget (name, key) returns the valueredis.hget ('price',' cake') 5hmget (name, keys, * args) corresponding to field in the hash whose key is name, and returns the valueredis.hmget ('price', [' apple', 'orange']) corresponding to each key in the hash whose key is name. The mapping redis.hmset (name, mapping) is added in batches to the hash where key is name. 'pear': 6}) Truehincrby (name, key, amount=1) adds value mapped in hash where key is name by amountredis.hincrby (' price', 'apple', 3) 6 The modified value hexists (name, key) key is whether there is a mapping with the key name key in namehash ('price',' banana') Truehdel (name, * keys) key is namehash, delete the mapping redis.hdel ('price',' banana') Truehlen (name) with the key name key, get the number of maps redis.hlen ('price') 6hkeys (name) from hash with key as name, get all mapping keys redis.hkeys (' price') [baked cake' from hash where key is name Bounded bookkeeping, baked bananas, baked pearl'] hvals (name) get all mapped keys redis.hvals ('price') [baked 5, baked 6, bounded 2, bounded 6'] hgetall (name) from name hash with key as name get all mapped key pairs redis.hgetall ('price') {baked cakeboxes: baked 5, baked bookstores: baked 6, bounded orangeholders: baked 7, baked pearls: baked 6'}

Note:

Hscan (name, cursor=0, match=None, count=None): incremental iterative acquisition is very useful for large data. Hscan can obtain data in pieces, not all the data at once, so the memory is burst.

Parameters: name cursor of name,redis, match of cursor (obtaining data based on cursor batch fetching) match, matching the specified key. Default None represents all key count, and the minimum number of shards is obtained per shard. Default None means the default number of shards using Redis, such as: first: cursor1, data1 = r.hscan ('xx', cursor=0, match=None, count=None) the second time: cursor2, data1 = r.hscan (' xx', cursor=cursor1, match=None, count=None)... Until the return value cursor is 0, it means that the data has been obtained by sharding.

Hscan_iter (name, match=None, count=None): use yield to encapsulate hscan to create a generator to obtain data from redis in batches

Parameter: match, which matches the specified key. Default None indicates all key count, and the minimum number of shards is obtained per shard. Default None means the default number of shards used in Redis, such as: for item in r.hscan_iter ('xx'): print item pipe

By default, redis-py creates (connection pooling requests for connections) and disconnects (returns connection pooling) for each request. If you want to specify multiple commands in one request, you can use pipline to specify multiple commands for one request, and pipline is atomic by default.

Import redispool = redis.ConnectionPool (host='10.211.55.4', port=6379) r = redis.Redis (connection_pool=pool) # pipe = r.pipeline (transaction=False) pipe = r.pipeline (transaction=True) pipe.multi () pipe.set ('name',' linwow') pipe.set ('age',' 18') pipe.execute () Django uses redis

Method 1:

Under the utils folder, create a redis_pool.py

Import redisPOOL = redis.ConnectionPool (host='127.0.0.1', port=6379,password='1234',max_connections=1000)

Use in the view function:

Import redisfrom django.shortcuts import render,HttpResponsefrom redis_pool import POOLdef index (request): conn = redis.Redis (connection_pool=POOL) conn.hset ('liwow','age',18) return HttpResponse (' set successfully') def order (request): conn = redis.Redis (connection_pool=POOL) conn.hget ('kkk','age') return HttpResponse (' get successful')

Method 2:

Install the django-redis module

Pip3 install django-redis

Configuration in setting:

# redis configuration CACHES = {"default": {"BACKEND": "django_redis.cache.RedisCache", "LOCATION": "redis://127.0.0.1:6379", "OPTIONS": {"CLIENT_CLASS": "django_redis.client.DefaultClient" "CONNECTION_POOL_KWARGS": {"max_connections": 100} # "PASSWORD": "123",}

View function:

From django_redis import get_redis_connectionconn = get_redis_connection ('default') print (conn.hgetall (' xxx')) what are the main application areas of python 1. Cloud computing, typical application OpenStack. 2. WEB front-end development, many large websites are developed by Python. 3. Artificial intelligence applications, which are based on big data's analysis and deep learning, have essentially been unable to leave python. 4. System operation and maintenance project, the standard configuration of automatic operation and maintenance is python+Django/flask. 5. Financial management analysis, quantitative transaction, financial analysis. 6. Big data's analysis.

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