user8728: With the probable increase in demand for multi-sig (P2SH) addresses, and since the procedure for creating such addresses requires that each participant provides the uncompressed public key for an address under their control, I find it surprising hard to find documentation on how to export the public key of a bitcoin address.
So for the benefit of future searches: How exactly to you get the public key for an existing address for which you have a private key in bitcoin-qt?

user1587: I'd like to give a general answer that can apply to any wallet. As long as you have the private key, you can get the public key easily.
You can convert any private key to a public key using pybitcointools. After you install pybitcointools using pip install pybitcointools, simply run python and issue the following commands:
import bitcoin
bitcoin.privtopub('57c617d9b4e1f7af6ec97ca2ff57e94a28279a7eedd4d12a99fa11170e94f5a4')

Of course, you will have to replace your private key in the above statement.

user8728: And the answer is:

copy the address in question from your "Receive" address list
Help -> Debug window -> Console
type: validateaddress <address>

where <address> is the address you copied in step 1.
The command validateaddress will output a number of key-value pairs, one of them being "pubkey".
Edit: bitcoin-qt creates compressed keys (as you can check in the iscompressed key-value). If you need uncompressed keys you can use something like https://coinb.in/

8728: <p>With the probable increase in demand for multi-sig (P2SH) addresses, and since the procedure for creating such addresses requires that each participant provides the uncompressed public key for an address under their control, I find it surprising hard to find documentation on how to export the public key of a bitcoin address.</p>

<p>So for the benefit of future searches: How exactly to you get the public key for an existing address for which you have a private key in bitcoin-qt?</p>
 1587: <p>I'd like to give a general answer that can apply to any wallet. As long as you have the private key, you can get the public key easily.</p>

<p>You can convert any private key to a public key using <a href="https://github.com/vbuterin/pybitcointools" rel="nofollow">pybitcointools</a>. After you install pybitcointools using <code>pip install pybitcointools</code>, simply run <code>python</code> and issue the following commands:</p>

<pre><code>import bitcoin
bitcoin.privtopub('57c617d9b4e1f7af6ec97ca2ff57e94a28279a7eedd4d12a99fa11170e94f5a4')
</code></pre>

<p>Of course, you will have to replace your private key in the above statement.</p>
 8728: <p>And the answer is:</p>

<ol>
<li>copy the address in question from your "Receive" address list</li>
<li>Help -> Debug window -> Console</li>
<li>type: <code>validateaddress &lt;address&gt;</code></li>
</ol>

<p>where <code>&lt;address&gt;</code> is the address you copied in step 1.</p>

<p>The command <code>validateaddress</code> will output a number of key-value pairs, one of them being <code>"pubkey"</code>.</p>

<p>Edit: bitcoin-qt creates compressed keys (as you can check in the <code>iscompressed</code> key-value). If you need uncompressed keys you can use something like <a href="https://coinb.in/" rel="noreferrer">https://coinb.in/</a></p>
