You are looking for the [`SCARD`][1] command:

&gt; ## `SCARD key`
&gt; Returns the set cardinality (number of elements) of the set stored at
&gt; 
&gt; **Return value**  
Integer reply: the cardinality (number of elements) of the set, or 0 if key does not exist.

You can view all of the set commands on [the documentation webpage][2].


  [1]: http://redis.io/commands/scard
  [2]: http://redis.io/commands#set

If it&#39;s a sorted set, you can use

    ZCOUNT myset -inf +inf

or

    ZCARD myset

What are the additional benefits of `&quot;use strict&quot;` other than preventing bad coding?  For instance, does it allow the script to run faster because the interpreter knows the code its optimized?

Benefits of &quot;Use Strict&quot; in JS

I have written a small API which uses the Node js &quot;restify&quot; framework. This API receives a request (actually anything after &quot;/&quot;) and then send that request to another server. Get the response back from server and passes the response back to original source of request. For this API I am using both restify server and client.

Below is that API code for better understanding.

    var apiServer = require(&#39;apiServer&#39;);
    apiServer.start();
    
    var restify = require(&#39;restify&#39;);
    var assert = require(&#39;assert&#39;);
    
    function onRequest(request, response, next)
    {
        var client = restify.createStringClient({ 
            url: &#39;http://example.com&#39;
        });
            
        client.get(&#39;/&#39; + request.params[0], function(err, req, res, data) {
            assert.ifError(err);
    
            response.setHeader(&#39;Content-Type&#39;, &#39;text/html&#39;);
            response.writeHead(res.statusCode);
            response.write(data);
            response.end();
        });
        next();
    }

    function start()
    {
        var server = restify.createServer();
        server.get(/^\/(.*)/, onRequest);
        server.listen(8888);
    
        console.log(&quot;Server has started.&quot;);
    }

    exports.start = start;

Now I need to know the difference between `response.write` and `response.send` of Node.js. Because with `response.write` I can set header and write in it but it is not possible to do anything with headers when I use `response.send`. When I use `response.send` with `setHeader()` or `writeHeader()` I get this error:

&lt;pre&gt;http.js:691
    throw new Error(&#39;Can\&#39;t set headers after they are sent.&#39;);
          ^
    Error: Can&#39;t set headers after they are sent.
&lt;/pre&gt;

There is also another thing. With `response.send()` I get the complete HTML output on the screen like:

    &lt;!DOCTYPE html&gt;\n&lt;html&gt;\n\t&lt;head&gt;&lt;/head&gt;&lt;/html&gt; ..... &quot;bla bla bla&quot;

But with `response.write` I do not get the html on screen but only the text `&quot;bla bla bla&quot;`.

It would be great if someone can explain me the differences.

Difference between response.send and response.write in node js

For lists I can do the operation:

    LLEN KeyName

and it will return the size of a list in Redis. What is the equivalent command for sets? I can&#39;t seem to find this in any documentation.

How do I get the size of a set on Redis?

<p>For lists I can do the operation:</p>
<pre><code class="hljs">LLEN KeyName
</code></pre>
<p>and it will return the size of a list in Redis. What is the equivalent command for sets? I can't seem to find this in any documentation.</p>


I have a Linux server with Redis installed and I want to connect to it via command line from my local Linux machine.

Is it possible to install `redis-cli` only (without `redis-server` and other tools)?

If I just copy `redis-cli` file to my local machine and run it, I have the following error:

    ./redis-cli: /lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.14&#39; not found (required by ./redis-cli)


Linux - Install redis-cli only

I&#39;m able to connect to an **[ElastiCache][1] Redis instance in a VPC** from **EC2 instances**. But I would like to know if there is a way to connect to an ElastiCache Redis node outside of Amazon EC2 instances, such as from my *local* dev setup or VPS instances provided by other vendors.

Currently when trying from my local set up:

    redis-cli -h my-node-endpoint -p 6379

I only get a timeout after some time.


  [1]: https://aws.amazon.com/elasticache/

Can you connect to Amazon ElastiСache Redis outside of Amazon?

I noticed that there are two different projects for using redis for django cache

https://github.com/sebleier/django-redis-cache/

https://github.com/niwibe/django-redis

Is one better known than the other, more of a standard package? I can&#39;t decide which to use.



Difference between django-redis-cache and django-redis for redis caching with Django?

I&#39;m writing a django management command to handle some of our redis caching. Basically, I need to choose all keys, that confirm to a certain pattern (for example: &quot;prefix:*&quot;) and delete them.

I know I can use the cli to do that:


    redis-cli KEYS &quot;prefix:*&quot; | xargs redis-cli DEL

But I need to do this from within the app. So I need to use the python binding (I&#39;m using py-redis). I have tried feeding a list into delete, but it fails:
 
  
    from common.redis_client import get_redis_client
    cache = get_redis_client()
    x = cache.keys(&#39;prefix:*&#39;) 
   
    x == [&#39;prefix:key1&#39;,&#39;prefix:key2&#39;] # True
   # And now
    
    cache.delete(x) 
   # returns 0 . nothing is deleted

I know I can iterate over x:


    for key in x:
       cache.delete(key)

But that would be losing redis awesome speed and misusing its capabilities. Is there a pythonic solution with py-redis, without iteration and/or the cli?

Thanks!


Redis Python - how to delete all keys according to a specific pattern In python, without python iterating

There is a post about a Redis command to get all available keys, but I would like to do it with Python.

Any way to do this?

Get all keys in Redis database with python

For lists, we use the `Collections.sort(List)` method. What if we want to sort a `HashSet`?

How to sort a HashSet?

For copying a list: `shallow_copy_of_list = old_list[:]`.

For copying a dict: `shallow_copy_of_dict = dict(old_dict)`.

But for a `set`, I was worried that a similar thing wouldn&#39;t work, because saying `new_set = set(old_set)` would give a set of a set?

But it does work. So I&#39;m posting the question and answer here for reference. In case anyone else has the same confusion.



How to clone or copy a set in Python?

I&#39;m working on a H.264 Decoder and I&#39;m wondering where to find the SPS and PPS. My reference literature tells me that those are NAL Units encoded in the H.264-Stream, but when I look into an example-MP4-File with IsoViewer, it says that the SPS and PPS are in the avcC Box. 

How exactly does this work? How does it look for .mkv files or other H.264 containers?

Possible Locations for Sequence/Picture Parameter Set(s) for H.264 Stream

[Given Zero Piraeus&#39; answer to another question](https://stackoverflow.com/a/26116307/1763356), we have that

    x = tuple(set([1, &quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;z&quot;, &quot;f&quot;]))
    y = tuple(set([&quot;a&quot;, &quot;b&quot;, &quot;c&quot;, &quot;z&quot;, &quot;f&quot;, 1]))
    print(x == y)

Prints `True` about 85% of the time with [hash randomization](http://lemire.me/blog/archives/2012/01/17/use-random-hashing-if-you-care-about-security/) enabled. Why 85%?

Why does tuple(set([1,&quot;a&quot;,&quot;b&quot;,&quot;c&quot;,&quot;z&quot;,&quot;f&quot;])) == tuple(set([&quot;a&quot;,&quot;b&quot;,&quot;c&quot;,&quot;z&quot;,&quot;f&quot;,1])) 85% of the time with hash randomization enabled?

I have a list of lists like this:

    i = [[1, 2, 3], [2, 4, 5], [1, 2, 3], [2, 4, 5]]

I would like to get a list containing &quot;unique&quot; lists (based on their elements) like:

    o = [[1, 2, 3], [2, 4, 5]]

I cannot use `set()` as there are non-hashable elements in the list. Instead, I am doing this:

    o = []
    for e in i:
      if e not in o:
        o.append(e)

Is there an easier way to do this?



Content Type	Original Author	Original Content on Stackoverflow
Question	Elijah	View Question on Stackoverflow
Solution 1 - Redis	Tim Cooper	View Answer on Stackoverflow
Solution 2 - Redis	Donald	View Answer on Stackoverflow

How do I get the size of a set on Redis?

Redis Problem Overview

Redis Solutions

Solution 1 - Redis

Solution 2 - Redis

Difference between response.send and response.write in node js

Benefits of "Use Strict" in JS

Attributions