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  19 <b>ExistsCommand: Contents
</b><br>  <a href=
"#EXISTS _key_">EXISTS _key_
</a><br>    <a href=
"#Return value">Return value
</a><br>    <a href=
"#See also">See also
</a> 
  22                 <h1 class=
"wikiname">ExistsCommand
</h1> 
  29                     <h1><a name=
"EXISTS _key_">EXISTS _key_
</a></h1> 
  30 <i>Time complexity: O(
1)
</i><blockquote>Test if the specified key exists. The command returns
"0" if the key exists, otherwise 
"1" is returned.Note that even keys set with an empty string as value willreturn 
"1".
</blockquote> 
  31 <h2><a name=
"Return value">Return value
</a></h2><a href=
"ReplyTypes.html">Integer reply
</a>, specifically:
<br/><br/><pre class=
"codeblock python" name=
"code"> 
  33 0 if the key does not exist.
 
  34 </pre><h2><a name=
"See also">See also
</a></h2> 
  35 <ul><li> <a href=
"SetnxCommand.html">SETNX
</a> is a 
<code name=
"code" class=
"python">SET if not EXISTS
</code> atomic operation.
</li><li> <a href=
"SismemberCommand.html">SISMEMBER
</a> test if an element is a member of a Set.
</li></ul>